Add a keyboard shortcut to change account (multiple accounts)

**Is your feature request related to a problem? Please describe.**
I have quite a few Fediverse accounts, each of them following different circles of people. I often want to view a lot of homepage timelines in a short period of time, or will find something on one account but want to share, favourite or reply to it from a different.

As it stands, clicking on avatar (top left of screen) → Accounts... (top left of screen) → a specific account (bottom centre of screen) feels like a lot of extraneous effort, especially when you're doing it four or five times every 10–30 minutes.

**Describe the solution you'd like**
It'd be handy if a keyboard shortcut could be added to move between accounts without having to go through menus.

For example, maybe pressing `a` switches to the next account in the list, before looping back around to the first. Extra points for if it maintains the current view when doing (feed, notification, post, etc.)

**Describe alternatives you've considered**
Use a different client that better supports multiple accounts at once, I guess. 🤷 I can't see any way of doing this easier, as it stands.

Thanks!