…' state

Get rid of the `overrides` in the minimize plugin.

We want to use the sidebar to show other things besides the occupants.

- Try to whittle down the color variables to the bare minimum.
- Remove unnecessary CSS variables.
- Thicker border around chat bottom panel

And move styles into more appropriate files.

- Add link to open chat from occupant view
- Add dropdown menu

So that `converse-chat-content` can be kept more generic.

Set the model directly on the `*-chat-content` components, instead of
passing in the JID, so that the component doesn't have to know where to
fetch the model from.

https://lit.dev/docs/templates/expressions/#invalid-locations

in the MUC sidebar.

Updates #698

Updates #698

I want to make it possible to add contacts with no presence
subscription, so technically contacts that aren't in the roster, so that
we can see them in the controlbox sidebar when we have chats open with
them.