Annotate unreachable comment-scanner switch paths to satisfy C26819 (#5071)

include/nlohmann/detail/input/lexer.hpp

diff --git a/include/nlohmann/detail/input/lexer.hpp b/include/nlohmann/detail/input/lexer.hpp
index 3d63229..4742d88 100644
--- a/include/nlohmann/detail/input/lexer.hpp
+++ b/include/nlohmann/detail/input/lexer.hpp
@@ -863,6 +863,8 @@
                             break;
                     }
                 }
+
+                JSON_HEDLEY_UNREACHABLE();
             }
 
             // multi-line comments skip input until */ is read
@@ -898,6 +900,8 @@
                             continue;
                     }
                 }
+
+                JSON_HEDLEY_UNREACHABLE();
             }
 
             // unexpected character after reading '/'

single_include/nlohmann/json.hpp

diff --git a/single_include/nlohmann/json.hpp b/single_include/nlohmann/json.hpp
index 7d68c5a..e2bb851 100644
--- a/single_include/nlohmann/json.hpp
+++ b/single_include/nlohmann/json.hpp
@@ -8055,6 +8055,8 @@
                             break;
                     }
                 }
+
+                JSON_HEDLEY_UNREACHABLE();
             }
 
             // multi-line comments skip input until */ is read
@@ -8090,6 +8092,8 @@
                             continue;
                     }
                 }
+
+                JSON_HEDLEY_UNREACHABLE();
             }
 
             // unexpected character after reading '/'