Breadcrumbs to the wiki (#5017)

* Breadcrumbs to the wiki

* Update README.md
diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index 543b586..45af0ea 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -207,7 +207,8 @@
 Contributing code
 -----------------
 
-We gladly accept contributions via GitHub pull requests.
+We gladly accept contributions via GitHub pull requests. See [the wiki](https://github.com/flutter/engine/wiki) for
+information about the engine's architecture.
 
 To start working on a patch:
 
diff --git a/README.md b/README.md
index e52c496..d38f794 100644
--- a/README.md
+++ b/README.md
@@ -28,6 +28,9 @@
 
  - For information about contributing code to the engine itself, please see
    [CONTRIBUTING.md](CONTRIBUTING.md).
+   
+ - For information about the engine's architecture, please see
+   [the wiki](https://github.com/flutter/engine/wiki).
 
 Community
 ---------