Refactor the C++ guidelines (#2178)

* Refactor the C++ guidelines
* Cleanup and adding TODOs
* Update the C++ sidebar links

.gitignore

@@ -14,3 +14,4 @@ _site/
 .idea
 .DS_Store
 vendor/
+/.vs

_data/sidebars/general_sidebar.yml

@@ -155,14 +155,19 @@ entries:
         url: /clang_documentation.html
   - title: C++ Guidelines
     folderitems:
-      - title: Introduction
+      - title: Design
         url: /cpp_introduction.html
-      - title: API Design
-        url: /cpp_design.html
       - title: Implementation
         url: /cpp_implementation.html
-      - title: Documentation
-        url: /cpp_documentation.html
+        subfolders:
+            - title: API Documentation
+              subfolderitems:
+                - title: azure-storage-blob
+                  external_url: https://azure.github.io/azure-sdk-for-cpp/storage.html#azure-storage-blob
+                - title: azure-storage-file-datalake
+                  external_url: https://azure.github.io/azure-sdk-for-cpp/storage.html#azure-storage-file-datalake
+                - title: azure-storage-file-share
+                  external_url: https://azure.github.io/azure-sdk-for-cpp/storage.html#azure-storage-file-shares
   - title: Go Guidelines
     folderitems:
       - title: Introduction