Support for `blue`

[MatthewScholefield]

I use blue formatter which is exactly like black but with a few modifications. Other language servers like Pylance allow customizing the black executable name so it can be changed to blue. I'm wondering if this project would be open to allowing a customization of the import name like black = __import__(config.import_name).

For now I will just create a fork and use that.

[haplo]

I didn't know about blue, love the logo! 😆

If all it takes for compatibility is to introduce a black_executable configuration option then I would be open to PRs for it. Otherwise a fork to python-lsp-blue would make more sense IMO.