support riot.js

[jens1o]

_Fixes #325_

Changes proposed:

• Add
• Prepare
• Delete
• Fix

Things I've done:

• I've pulled the latest master branch
• I've run npm install to install all the dependenies
• I've checked my code, it is clean.
• I've run ESLint.
• My pull request fixes an issue, I referenced the issue.
• My pull request is not too big, otherwise I've already squashed it.
• I've run npm run build to build the extension. (If I had done something with the extension.)

adds riot.js with jade icon