Show MR Activity in a new "tab"

## Feature Description
The Gitlab Overview page shows the "Activity" including MR renames, commits, review requests, approvals, etc. An example:


I'd find it helpful if this information was also shown in `gitlab.nvim`. I imagine it could be another "tab" next to "Comments" and "Notes".

I think this should not even be that difficult to prepare a simple listing of the items. I can imagine it would be useful to make it interactive by e.g., enabling to easily show the commits or diffs just like Gitlab makes the commit hashes clickable and adds a "Compare with previous version" button. This might even be useful as a workaround for #450.