Add link to Matrix community space in-app

[soupslurpr]

In the absence of a website for Transcribro like BeauTyXT has, it'd be good to include the link to the Matrix community space in the app so people can have a clear way of getting support instead of having to click on the source code link and look through the README because they probably won't do it since it isn't obvious the Matrix community space's link can be obtained from trying to view the source code.

It should be the first entry in the About section of the settings because it's important.