Add WorkspaceFoldersClientCapabilites

[MariaSolOs]

Closes microsoft/language-server-protocol#2133

Complements microsoft/language-server-protocol#2134 which contains the respective updates to the specification.

[dbaeumer]

@MariaSolOs can you explain why you think this is necessary. The assumption was always that if a client has support for workspace folders it also supports change notifications. If we add the client capability it might break existing servers since they instead of a boolean receive a object literal.

[MariaSolOs]

@MariaSolOs can you explain why you think this is necessary. The assumption was always that if a client has support for workspace folders it also supports change notifications. If we add the client capability it might break existing servers since they instead of a boolean receive a object literal.

My main motivation here is being able to announce client support for dynamically registering to receive workspace/didChangeWorkspaceFolders notifications. This aligns with the client capabilities of other requests (e.g. CodeLensClientCapabilities).

[dbaeumer]

I think we should still be able to allow for registering without breaking servers. We could offer a different route for this if it is necessary.

[MariaSolOs]

I think we should still be able to allow for registering without breaking servers. We could offer a different route for this if it is necessary.

Fair enough. I'm open to suggestions on how to include the necessary dynamicRegistration support information in a backwards compatible way.