desktop: Add "Open .livebookdesktop.sh|bat" menu item

[wojtekmach]

This is especially useful for the ZTA feature because we need to set LIVEBOOK_IDENTITY_PROVIDER somewhere.

I've updated nightlies with this branch:

• macOS
• Windows

Demo on macOS:

Demo on Windows:

[wojtekmach]

cc @mat-hek

[github-actions]

Uffizzi Preview deployment-36680 was deleted.

[wojtekmach]

I just realised we might be able to have a ~/.livebookdesktop.exs instead. It would work like a config/runtime.exs. I think the benefit would be we'd have same syntax for all platforms. On the flip side maybe it would be awkward to write there:

System.put_env("LIVEBOOK_PORT", "9999")

whereas users might have expected a more Elixir-centric API, e.g.: config :livebook, ....

All this being said perhaps it is not easy or impossible to make it work, e.g. the file would have been evaluated too late.

[josevalim]

This is great. I have added some suggestions to the generated files. :)