Switch to relative paths in app manifest (#36)

## Motivation for the change, related issues

We want to host a private Playground instance and are seeking to
eliminate places where `playground.wordpress.net` is hard-coded. It
turns out that URLs within app manifests can be relative, so we can
remove mention of playground.wordpress.net from manifest.json.

## Implementation details

This PR:
- Converts paths in manifest.json to relative paths
- Removes the manifest-related operations in the build step because both
the built website and the dev version (via `npm run dev`) are
installable as PWAs
- Moves `manifest.json` into the website package's `public/` folder so
Vite stops moving and mangling the filename.

## Testing Instructions (or ideally a Blueprint)

- CI

Test built app:
- Run `npx nx build playground-website`
- Run `php -S 127.0.0.1:7778 -t
dist/packages/playground/wasm-wordpress-net` to start a web server
- Visit `https://127.0.0.1:7778` in Chrome and note the site is
installable as a PWA

Test dev:
- Run `npm run dev`
- Visit the dev site in Chrome and note the site is installable as a PWA

Author: brandonpayton

packages/playground/website/manifest.json renamed to packages/playground/website/public/manifest.json

@@ -2,31 +2,31 @@
 	"theme_color": "#ffffff",
 	"background_color": "#ffffff",
 	"display": "standalone",
-	"scope": "https://playground.wordpress.net/",
-	"start_url": "https://playground.wordpress.net/",
+	"scope": "/",
+	"start_url": "/",
 	"short_name": "WordPress Playground",
 	"description": "WordPress Playground",
 	"name": "WordPress Playground",
 	"icons": [
 		{
-			"src": "https://playground.wordpress.net/logo-192.png",
+			"src": "logo-192.png",
 			"sizes": "192x192",
 			"type": "image/png"
 		},
 		{
-			"src": "https://playground.wordpress.net/logo-256.png",
+			"src": "logo-256.png",
 			"sizes": "256x256",
 			"type": "image/png"
 		},
 		{
-			"src": "https://playground.wordpress.net/logo-384.png",
+			"src": "logo-384.png",
 			"sizes": "384x384",
 			"type": "image/png"
 		},
 		{
-			"src": "https://playground.wordpress.net/logo-512.png",
+			"src": "logo-512.png",
 			"sizes": "512x512",
 			"type": "image/png"
 		}
 	]
-}
+}

packages/playground/website/vite.config.ts

@@ -20,7 +20,6 @@ import { copyFileSync, existsSync } from 'node:fs';
 import { join } from 'node:path';
 import { buildVersionPlugin } from '../../vite-extensions/vite-build-version';
 import { listAssetsRequiredForOfflineMode } from '../../vite-extensions/vite-list-assets-required-for-offline-mode';
-import { addManifestJson } from '../../vite-extensions/vite-manifest';
 import virtualModule from '../../vite-extensions/vite-virtual-module';
 
 const proxy: CommonServerOptions['proxy'] = {
@@ -131,14 +130,6 @@ export default defineConfig(({ command, mode }) => {
 					}
 				},
 			} as Plugin,
-			/**
-			 * Add `manifest.json` file to the `dist/` directory when building.
-			 * While in development, modify the `manifest.json` file to use the local
-			 * server URL.
-			 */
-			addManifestJson({
-				manifestPath: path('./manifest.json'),
-			}) as Plugin,
 			/**
 			 * Generate a list of files needed for the website to function offline.
 			 */