Store server list outside project

Currently I believe the list of servers offered in this menu:

is stored only in `backstitch.cfg` `[backstitch]available_servers` in each project.

If I have used https://backstitch.endlessstudios.com/ in one project, it is likely that I would like to use it in another project. Perhaps this list could be stored in the editor settings rather than in `backstitch.cfg`?

Start by locating the code that reads `backstitch.cfg` `[backstitch]available_servers` and builds the server-selection menu, then inspect how editor settings are stored. The change is done when a server configured through editor settings appears across projects without requiring each project’s `backstitch.cfg` to contain the list.

Written by the indexing model from the issue text.