feat(dev-infra): standard CLI commands using yargs (#36326)

Creates a standard model for CLI commands provided by ng-dev.
Allows for us to have any of the tools/scripts extend to be
included in the ng-dev command, or be standalone using the same
yargs parser.

PR Close #36326

dev-infra/pullapprove/cli.ts

@@ -0,0 +1,19 @@
+/**
+ * @license
+ * Copyright Google Inc. All Rights Reserved.
+ *
+ * Use of this source code is governed by an MIT-style license that can be
+ * found in the LICENSE file at https://angular.io/license
+ */
+import * as yargs from 'yargs';
+import {verify} from './verify';
+
+/** Build the parser for the pullapprove commands. */
+export function buildPullapproveParser(localYargs: yargs.Argv) {
+  return localYargs.help().strict().demandCommand().command(
+      'verify', 'Verify the pullapprove config', {}, () => verify());
+}
+
+if (require.main === module) {
+  buildPullapproveParser(yargs).parse();
+}