Add chat members to the chat info

[yuraiz]

[melix99]

Please consider reorganizing the commit history a bit. Currently it's a bit messy.

For example, consider creating a commit for each feature/bug fix/structural change instead of creating one commit every time you make a change in a file.

[melix99]

So, there are some things about the implementation that can definitely be improved.

First, the ChatMember gobject is basically useless because it doesn't have properties. Actually, I think that it doesn't even need to be a gobject at all because it seems that these objects can't be updated from tdlib at all, so I suggest creating a Boxed type instead (see tdlib/mod.rs).

Then, I suggest moving the get_supergroup_members inside Supergroup via a new async members() function. This should probably return a GListStore of the boxed ChatMember type.

[melix99]

Design-wise I think I'd prefer not having a AdwViewSwitcher in the ChatInfoWindow, also because we'll have many more items in the future. What about creating a row like that: