update installation instructions and add mpv handler setup script

package.json

@@ -5,8 +5,13 @@
   "description": "Web-first PWA media player that integrates with Hydrus",
   "scripts": {
     "dev": "vite",
+    "start": "vite",
     "build": "vite build",
     "preview": "vite preview",
+    "typecheck": "tsc --noEmit",
+    "setup:mpv-handler": "node ./scripts/setup-mpv-handler.mjs",
+    "install:mpv-handler": "npm run setup:mpv-handler",
+    "uninstall:mpv-handler": "powershell -NoProfile -ExecutionPolicy Bypass -File .\\scripts\\uninstall-mpv-handler.ps1",
     "format": "prettier --write \"src/**/*.{ts,tsx,js,jsx,json,css,md}\""
   },
   "dependencies": {