Support offline mode

[james5635]

The extension is not working in offline. The omnisharp need update.
It works only when I have internet.

Language server omnisharp:

from extension "C#" version 0.1.3: error fetching latest release

Caused by:
    0: error sending request for url (https://api.github.com/repos/OmniSharp/omnisharp-roslyn/releases)
    1: client error (Connect)
    2: dns error: failed to lookup address information: Temporary failure in name resolution
    3: failed to lookup address information: Temporary failure in name resolution

[kevin-mueller]

I second this. It feels very strange that I have to be connected to the internet to use a text editor.

[mariansimecek]

I think Zed needs to support this zed-industries/zed#24878