:memo: add more API documentation

diff --git a/doc/docset/docSet.sql b/doc/docset/docSet.sql
index b483940..93fd478 100644
--- a/doc/docset/docSet.sql
+++ b/doc/docset/docSet.sql

@@ -78,6 +78,8 @@
 INSERT INTO searchIndex(name, type, path) VALUES ('operator+=', 'Operator', 'api/basic_json/operator+=/index.html');
 INSERT INTO searchIndex(name, type, path) VALUES ('operator=', 'Operator', 'api/basic_json/operator=/index.html');
 INSERT INTO searchIndex(name, type, path) VALUES ('operator==', 'Operator', 'api/basic_json/operator==/index.html');
+INSERT INTO searchIndex(name, type, path) VALUES ('operator<', 'Operator', 'api/basic_json/operator</index.html');
+INSERT INTO searchIndex(name, type, path) VALUES ('operator>', 'Operator', 'api/basic_json/operator>/index.html');
 INSERT INTO searchIndex(name, type, path) VALUES ('operator[]', 'Operator', 'api/basic_json/operator[]/index.html');
 INSERT INTO searchIndex(name, type, path) VALUES ('operator""_json', 'Literal', 'api/basic_json/operator_literal_json/index.html');
 INSERT INTO searchIndex(name, type, path) VALUES ('operator""_json_pointer', 'Literal', 'api/basic_json/operator_literal_json_pointer/index.html');

diff --git a/doc/mkdocs/docs/api/basic_json/index.md b/doc/mkdocs/docs/api/basic_json/index.md
index cdc7f94..ff00525 100644
--- a/doc/mkdocs/docs/api/basic_json/index.md
+++ b/doc/mkdocs/docs/api/basic_json/index.md

@@ -81,9 +81,9 @@
 | `const_pointer`          | `#!cpp std::allocator_traits<allocator_type>::const_pointer` |
 | `iterator`               | [LegacyBidirectionalIterator](https://en.cppreference.com/w/cpp/named_req/BidirectionalIterator) |
 | `const_iterator`         | constant [LegacyBidirectionalIterator](https://en.cppreference.com/w/cpp/named_req/BidirectionalIterator) |
-| `reverse_iterator`       |  |
-| `const_reverse_iterator` |  |
-| `iteration_proxy`        |  |
+| `reverse_iterator`       | reverse iterator, derived from `iterator` |
+| `const_reverse_iterator` | reverse iterator, derived from `const_iterator` |
+| `iteration_proxy`        | helper type for [`items`](items.md) function |
 
 ### JSON value data types
 
@@ -193,9 +193,9 @@
 
 - [**operator==**](operator==.md) - comparison: equal
 - [**operator!=**](operator!=.md) - comparison: not equal
-- operator< - comparison: less than
+- [**operator<**](operator<.md) - comparison: less than
 - operator<= - comparison: less than or equal
-- operator> - comparison: greater than
+- [**operator>**](operator>.md) - comparison: greater than
 - operator>= - comparison: greater than or equal
 
 ### Serialization

diff --git "a/doc/mkdocs/docs/api/basic_json/operator\074.md" "b/doc/mkdocs/docs/api/basic_json/operator\074.md"
new file mode 100644
index 0000000..e8d2fb3
--- /dev/null
+++ "b/doc/mkdocs/docs/api/basic_json/operator\074.md"

@@ -0,0 +1,73 @@
+# basic_json::operator<
+
+```cpp
+bool operator<(const_reference lhs, const_reference rhs) noexcept,
+
+template<typename ScalarType>
+bool operator<(const_reference lhs, const ScalarType rhs) noexcept;
+
+template<typename ScalarType>
+bool operator<(ScalarType lhs, const const_reference rhs) noexcept;
+```
+
+Compares whether one JSON value `lhs` is less than another JSON value `rhs` according to the following rules:
+
+- If `lhs` and `rhs` have the same type, the values are compared using the default `<` operator.
+- Integer and floating-point numbers are automatically converted before comparison
+- Discarded values a
+- In case `lhs` and `rhs` have different types, the values are ignored and the order of the types is considered, which
+  is:
+    1. null
+    2. boolean
+    3. number (all types)
+    4. object
+    5. array
+    6. string
+    7. binary
+
+    For instance, any boolean value is considered less than any string.
+
+## Template parameters
+
+`ScalarType`
+:   a scalar type according to `std::is_scalar<ScalarType>::value`
+
+## Parameters
+
+`lhs` (in)
+:   first value to consider 
+
+`rhs` (in)
+:   second value to consider 
+
+## Return value
+
+whether `lhs` is less than `rhs`
+
+## Exception safety
+
+No-throw guarantee: this function never throws exceptions.
+
+## Complexity
+
+Linear.
+
+## Example
+
+??? example
+
+    The example demonstrates comparing several JSON types.
+        
+    ```cpp
+    --8<-- "examples/operator__less.cpp"
+    ```
+    
+    Output:
+    
+    ```json
+    --8<-- "examples/operator__less.output"
+    ```
+
+## Version history
+
+- Added in version 1.0.0.

diff --git "a/doc/mkdocs/docs/api/basic_json/operator\076.md" "b/doc/mkdocs/docs/api/basic_json/operator\076.md"
new file mode 100644
index 0000000..b9e3262
--- /dev/null
+++ "b/doc/mkdocs/docs/api/basic_json/operator\076.md"

@@ -0,0 +1,58 @@
+# basic_json::operator>
+
+```cpp
+bool operator>(const_reference lhs, const_reference rhs) noexcept,
+
+template<typename ScalarType>
+bool operator>(const_reference lhs, const ScalarType rhs) noexcept;
+
+template<typename ScalarType>
+bool operator>(ScalarType lhs, const const_reference rhs) noexcept;
+```
+
+Compares whether one JSON value `lhs` is greater than another JSON value `rhs` by calculating `#!cpp !(lhs <= rhs)`.
+
+## Template parameters
+
+`ScalarType`
+:   a scalar type according to `std::is_scalar<ScalarType>::value`
+
+## Parameters
+
+`lhs` (in)
+:   first value to consider 
+
+`rhs` (in)
+:   second value to consider 
+
+## Return value
+
+whether `lhs` is greater than `rhs`
+
+## Exception safety
+
+No-throw guarantee: this function never throws exceptions.
+
+## Complexity
+
+Linear.
+
+## Example
+
+??? example
+
+    The example demonstrates comparing several JSON types.
+        
+    ```cpp
+    --8<-- "examples/operator__greater.cpp"
+    ```
+    
+    Output:
+    
+    ```json
+    --8<-- "examples/operator__greater.output"
+    ```
+
+## Version history
+
+- Added in version 1.0.0.

diff --git a/doc/mkdocs/mkdocs.yml b/doc/mkdocs/mkdocs.yml
index 3310bd7..272ee5f 100644
--- a/doc/mkdocs/mkdocs.yml
+++ b/doc/mkdocs/mkdocs.yml

@@ -146,6 +146,8 @@
         - api/basic_json/operator=.md
         - api/basic_json/operator==.md
         - api/basic_json/operator!=.md
+        - api/basic_json/operator<.md
+        - api/basic_json/operator>.md
         - api/basic_json/operator+=.md
         - api/basic_json/operator_literal_json.md
         - api/basic_json/operator_literal_json_pointer.md