[Suggestion] Look for an already-existing zls binary instead of failing when internet is not avialable

[fluffymariline]

Problem

This extension currently requires internet to function, as the check for the zls version assumes internet is available.

Potential solution

The extension could check for existing zls binaries, either system-wide or installed previously by the extension, if it fails to connect to Github to check for the latest zls release, removing the requirement for internet when zls has already been downloaded.

[notpeter]

I've been meaning to pick this up and submit PRs to a bunch of extension repos to fix this.

See:

• Zed checks for LSP updates when offline and disables LSPs irreversibly in the process zed-industries/zed#9789