This adds a new option to the right click menu for git blame entries in
the gutter: "Open permalink". If there is a URL for the code host, then
this will open it.

Release Notes:

- Added "Open permalink" option to right-click menu of git blame entries
in gutter.

Demo:

![screenshot-2024-05-13-09 39
48@2x](https://github.com/zed-industries/zed/assets/1185253/656c177c-79f0-4a40-8838-7e963d099479)