API Documentation (#10)

* API documentation: Actions

* API documentation: Parser documentation

* Update action.md formatting

Author: ishuah

_data/sidebar.yml

@@ -38,6 +38,14 @@ menu:
 
       - page: Errors
         url: /errors
+
+  - links:
+      - page: API
+        url: /api
+      - page: Actions
+        url: /api/actions
+      - page: Parsers
+        url: /api/parsers
 
   - links:
       - page: Blog