[Website] Remove client package from the list of offline mode assets (#2841)

## Motivation for the change, related issues

When loading Playground I noticed an _Uncaught (in promise) TypeError:
Failed to execute 'addAll' on 'Cache': Request failed_ error caused by
offline mode caching.
The error was triggered because _blueprints-DY7omvFh.cjs_ and
_blueprints-Dg6flSLH.js_ are located in the `/client/` subdirectory on
Playground.WordPress.net while the [list of offline mode
assets](https://playground.wordpress.net/assets-required-for-offline-mode.json)
expects these files to be in the root folder.

To address the issue, this PR removes the _client_ package from the list
of offline assets.
We are also removing the _php-playground.html_ page from the list
because it depends on the client package but isn't part of the web
version of Playground.

## Testing Instructions (or ideally a Blueprint)

- Follow the [Test offline support
instructions](https://github.com/WordPress/wordpress-playground/blob/trunk/README.md#test-offline-support)
and ensure offline mode is working

Author: bgrgicak

packages/playground/website/vite.config.ts

@@ -151,7 +151,7 @@ export default defineConfig(({ command, mode }) => {
 			 */
 			listAssetsRequiredForOfflineMode({
 				outputFile: 'assets-required-for-offline-mode.json',
-				distDirectoriesToList: ['./', '../remote', '../client'],
+				distDirectoriesToList: ['./', '../remote'],
 			}) as Plugin,
 
 			/**

packages/vite-extensions/vite-list-assets-required-for-offline-mode.ts

@@ -8,9 +8,9 @@ const patternsToNotCache = [
 	/**
 	 * Static files that are not needed for the website to function offline.
 	 */
-	'/package.json',
-	'/README.md',
-	'/.DS_Store',
+	/\/package\.json$/i,
+	/\/README\.md$/i,
+	/\.DS_Store$/i,
 	'/index.cjs',
 	/\/.*\.d\.ts$/, // No type declarations are needed at runtime.
 	/\/lib\/.*/, // Remote lib files
@@ -73,6 +73,8 @@ const patternsToNotCache = [
 	 * Optional chunks are placed in assets/optional/ via vite.config.ts manualChunks configuration.
 	 */
 	/^\/assets\/optional\/.*/, // All optional assets (CodeMirror, language extensions, etc.)
+	/^\/client\/.*/, // Client package files arent't used by the web version of Playground
+	'/php-playground.html', // The PHP playground is a separate page that is not part of the web version of Playground
 ];
 
 function listFiles(dirPath: string, fileList: string[] = []) {
@@ -115,10 +117,7 @@ export const listAssetsRequiredForOfflineMode = ({
 				return listFiles(absoluteDirPath)
 					.map((file) => {
 						file = file.replace(absoluteDirPath, '');
-						if (file.startsWith('/')) {
-							return file;
-						}
-						return `/${file}`;
+						return join('/', file);
 					})
 					.filter((item) => {
 						return !patternsToNotCache.some((pattern) => {