Also install PHP dependencies

[ocean90]

We already install the JS dependencies but not the ones defined in composer.json for PHP.

js/packages/wordpress-plugin-boilerplate/lib/commands/create.js

Lines 238 to 241 in 5792ace

	// Install dependencies.
	await runStep( 'Installing dependencies', 'Could not install dependencies.', async () => {
	await runShellCommand( 'npm install', pluginDir );
	} );