Add intra-app pill link action to matrix.to links

[bkil]

It is useful to be able to share permalinks to people outside matrix by showing matrix.to links that I can right-click to copy the URL for them.

However, as a user of Matrix Static view, I can't navigate such permalinks within the site if I don't resolve matrix.to (or have http-links disabled, etc). Please add an onclick handler that opens the respective screen and/or scrolls to the referenced message or an equivalent fallback without JavaScript (e.g., either always rewrite such URL to point within view or perhaps include the original link in parenthesis).

This affects at least user submitted matrix.to links, room and user pills and generated references to the message and the user hidden behind the In reply to header.

Related: #113 element-hq/hydrogen-web#1104 matrix-org/matrix-viewer#236