Give the option to open a post/toot as another account

[strk]

When using a multi-account setup it's common to want to interact with a post from different accounts ( maybe to boost it or fav it or bookmark it ). The Tusky app gives a per-post menu item to "open as". I find that label not intuitive but the functionality is very very useful.

See also https://github.com/mastodon/mastodon-android/issues/471#issuecomment-1826721063

[realpixelcode]

Duplicate of #58