Enable workspace capabilites

[haukot]

They are enabled in Copilot.vim https://github.com/github/copilot.vim/blob/1358e8e45ecedc53daf971924a0541ddf6224faf/autoload/copilot/agent.vim#L536

[danp]

Just curious: what are the implications of this change?

[haukot]

@danp As I understand, in the first place it enables the support of workspace notifications(e.g. workspace/workspaceFolders, workspace/didChangeWatchedFiles). But Vim(and Emacs) copilot plugin doesn't send them.
So maybe it was part of a not implemented yet feature, or maybe it'll provide some support of workspaces(e.g. based on relativeFile property).