Uses Matrix's preview API to generate embedded link previews.
Only title and description for now.

Replace the custom Placeholder + BusyIndicator with the new LoadingPlaceholder component.
Also remove the "Loading…" page title on first load, as that is redundant to the existing front-and-center "Loading…" message and hence doesn't look nice.
When using Breeze light:
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This commit adds the ability to set the master push rule and set push rules for individual rooms as per the matrix spec. See https://spec.matrix.org/v1.3/client-server-api/#push-rules.
The master push rule is just on/off and uses the existing notification setting in general setting to enable/disable the server default master push rule .m.rule.master.
For each room there is now a page in the room setting that allows the following to be set:
- Default
- All messages
- @mentions and keywords
- off
New room or override rules are added/removed to achieve this.
There is also functionality to check the master/room notification state whenever the setting menu is entered. This allows the status to be updated if changed in another client or get the initial state for a room as it isn't stored.
Note - There is currently no menu items in the room list for setting the room push rule settings. This will be added in a later commit, the aim is to focus on making sure the technical implementation is good for now.
This started off as me just wanting to adjust the margin of the search bar but grew a touch ...
- Cleanup margins especially make the member search bar have the same padding as everything else
- Move room information title to header and align all buttons right.
- Make the room name actually bold
- Remove highlight from the user list item after the menu is closed
- Always use actual width so that the drawer isn't wider when modal
- Use control instead of pane for the search bar as the padding works more consistently
- Use BasicListItem instead of AbstractListItem for the member list as this has the layout predefined
