Feat: need to add a Popular themes section #165

In the docs repo, we have a section for 'Popular Extensions', just below it we can have a 'Popular Themes' section.
This will help users to quickly get some of the most popular and beautiful themes, without spending too much time by downloading and trying out themes themselves.

Here: a list is being maintained of all the themes that should be added to docs.

1. 'Themes for Brackets' by Jacse
   --- more to be added ---