Render blame info in the Source Viewer (fallback viewers)

Summary

In #430950 (closed) we added the ability to render blame information in the Source Viewer with the Highlight.js viewers.

This issue is about rendering the blame information for our Fallback viewers.

What are fallback viewers?

1. Any language that is not supported by Highlight.js
2. Any file type that is listed as a fallback

Possible solutions

I suggest looking into a "catch all" solution instead if trying to make it work per fallback. (e.g. any time the _text.haml viewer is used).