Add support for message search

[Igetin]

It appears this AppImage build of Element does not support message search. From the settings:

Same as text:

Element is missing some components required for securely caching encrypted messages locally. If you'd like to experiment with this feature, build a custom Element Desktop with search components added.

This is an essential feature for me, so I would really like to see it added. I’m running Fedora, which is not supported by the official Element releases. The web client can still be used, but message search is not supported there.