fix(testing): install devkit when init playwright

playwright generated config uses `@nx/devkit` which is not installed via playwright plugin
This usually works bc devkit is installed, but when using nx global install with
playwright an error is through saying it cannot find devkit

packages/playwright/src/generators/init/init.ts

@@ -23,6 +23,8 @@ export async function initGenerator(tree: Tree, options: InitGeneratorSchema) {
         {},
         {
           '@nx/playwright': nxVersion,
+          // required since used in playwright config
+          '@nx/devkit': nxVersion,
           '@playwright/test': playwrightVersion,
         }
       )