Display active account when performing visible actions #1637
Description
When multiple accounts are signed in, currently you can only tell which account is active from one of the top-level screens (where the hamburger menu is accessible and includes the account switcher).
If I open a link to an issue and want to comment, there's no indication as to which account I last used and is therefore active, and without the menu I have to navigate up 4 steps (issue → issues → repo → owner → home) in order to check.
It would be useful to surface the active account in more places, such as showing its avatar as part of issue forms, comment fields etc. -- even better if it can act as a switcher, or have something like the News Feed screen's user/org switcher to quickly select the right account.