matrix .well-known
With matrix switching from perspectives and self-signed certificates we will require using a valid cert for f-droid.org. This can be delegated to matrix.f-droid.org using a server .well-known file, to not require the certificate files to be on the matrix.f-droid.org subdomain.
Additionally I added the .htaccess file to set the allow origin header for the client .well-known file, as discussed in the previous MR.