gopls/internal/lsp: announce selectionRangeProvider capability

The server needs to tell the client it's supporting this feature.

Updates golang/go#36679

Change-Id: Ia6fdb35ea90fac81367d4b45721928c606344afc
Reviewed-on: https://go-review.googlesource.com/c/tools/+/458199
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Hyang-Ah Hana Kim <hyangah@gmail.com>
gopls-CI: kokoro <noreply+kokoro@google.com>
Reviewed-by: Robert Findley <rfindley@google.com>

gopls/internal/lsp/general.go

@@ -159,6 +159,7 @@ See https://github.com/golang/go/issues/45732 for more information.`,
 			InlayHintProvider:         protocol.InlayHintOptions{},
 			ReferencesProvider:        true,
 			RenameProvider:            renameOpts,
+			SelectionRangeProvider:    protocol.SelectionRangeRegistrationOptions{},
 			SignatureHelpProvider: protocol.SignatureHelpOptions{
 				TriggerCharacters: []string{"(", ","},
 			},