Adds maplibre as a dependency, and behind a labs flag, lets users send and receive [MSC3488](https://github.com/matrix-org/matrix-doc/blob/matthew/location/proposals/3488-location.md) style location shares - with backwards compatibility with old school `m.location` `msgtype` location shares too.
For this to work, you have to define a valid maptile server and API in your config.json's `map_style_url`.
We're anticipating development of polls soon, so for efficiency reasons we're getting the labs flag in early. If something goes wrong with the plan, this whole change will be reverted.
This removes all images we no longer reference in the app. This should be safe,
as Webpack only adds images to the build output if they are referenced.
