Declare workspaceFolders support in server capabilities (#4666)

* Declare workspaceFolders support in server capabilities

The `vscode-languageserver-node` dependency will attempt dynamic
capability registration for workspace folder change notifications
if this `workspace.workspaceFolders.changeNotifications` is not set
in the `InitializeResult`. That is problematic for clients that don't
support dynamic capability registration: if we send a JSONRPC error,
the server will exit because of the rejected promise.

The server has support for workspace folders and requests and uses
change notifications as far as I can see, so I believe it's more
correct to declare support for these up-front anyways.

* Fix formatting

---------

Co-authored-by: Heejae Chang <1333179+heejaechang@users.noreply.github.com>
Co-authored-by: Eric Traut <eric@traut.com>

packages/pyright-internal/src/languageServerBase.ts

@@ -756,6 +756,12 @@ export abstract class LanguageServerBase implements LanguageServerInterface {
                     workDoneProgress: true,
                 },
                 callHierarchyProvider: true,
+                workspace: {
+                    workspaceFolders: {
+                        supported: true,
+                        changeNotifications: true,
+                    },
+                },
             },
         };