Basic support for opam switch

[Khady]

fix #3

[Khady]

Is there anything required on my side to get this PR merged? No pressure, just that I've not contributed to zed's extensions before so I'm not sure of the process.

[notpeter]

Hi @Khady sorry for the delay. The lack of daily ocaml users on the Zed team plus the holiday means it slipped past most potential reviewers radar, thanks for the ping.

The error if you have opam installed but not ocaml-language-server is a bit opaque in the logs:

[ERROR] Command not found 'ocamllsp'

I don't think it's possible with the current Extension API to execute an arbitrary command and alter behavior (e.g. if opam list --short --installed --field-match=name:ocaml-lsp-server returns false output a custom error message which suggests running opam install -y ocaml-lsp-server). Perhaps a note in the doc is sufficient. I'll take a crack at that.

Otherwise looks good!

[Khady]

Thanks for your help!