Add support for multi workspace workflow

[wokalski]

This PR contains changes needed for multi folder workspaces support. Unfortunately I'm struggling to debug an issue with it. When you open a workspace with at least two folders, the plugin correctly creates a second client for the folder but every subsequent edit for files inside the second folder ends up with:

Notification handler 'textDocument/publishDiagnostics' failed with message: Illegal argument: character must be non-negative

Does it ring a bell?

[ManasJayanth]

@wokalski Anything else in the logs? What is the LSP server sending you? Just to get an idea. Things are moving fast with the language server too

[wokalski]

I didn’t have time to investigate further. But it seems like an issue on this end. I’ll debug when I come back from vacation.

[wokalski]

But nothing else is in the logs. There might be something wrong with the caching logic and maybe the extension winds up using the same lsp server for both workspace folders

[ManasJayanth]

This will probably close #30

[wokalski]

I'm gonna take a look at this now.

[wokalski]

I'll wait for #36 with this because I have a gut feeling they might be related.