message: fix: don't ask for goals of non-lean4 files
diff: @@ -70,6 +70,9 @@ export async function activate(context: ExtensionContext): Promise<any> {
  // I tried using languages.onDidChangeDiagnostics, which yields `language client not ready yet` errors.
  // Maybe this is fixed for a newer version of the LSP client, I don't know.
  window.onDidChangeTextEditorSelection(async e => {
  + if (e.textEditor?.document?.languageId !== 'lean4') {
  + return
  + }
  if (!e.selections) {
  infoView.wipeGoalsIfOpen()
  return
  