Tilenk/update rich text docs (#8)

Author: tilenkavcic

docs/supported_types.md

@@ -17,7 +17,8 @@ DevRev supports the following types:
   - Rich text is used in DevRev to represent text fields that can be formatted and can contain mentions. Eg.: description of an issue, body of a conversation, etc.
   - A simple rich text looks like one markdown string wrapped in an array: `["Hello **world**!"]`.
     Markdown should be compatible with [CommonMark Spec v0.30](https://spec.commonmark.org/0.30).
-  - To support mentions `rich_text` can be formatted as an array of strings and mention objects like so:  
+  - To support mentions `rich_text` can be formatted as an array of strings and mention objects. The field should also use the *use rich text* transformation method.
+  - Example of a simple mention object:  
     ```json
     [
       "Hello ",