Update the browser extension description in the Chrome and Firefox stores

Created by: AlicjaSuska

Part of RFC 221: Improve discoverability/awareness of the browser extension

Description

Add information about permissions and private code settings to the Chrome Web Store description and Mozilla add-ons marketplace.

Design documentation

Add information from ‘Make it work on your code host’ and ‘Make it work on private code’ sections from the installation page
Update screenshots (currently used ones are outdated)
Add a list of bundled extensions to the Firefox add-on description

Questions to answer