fix: add PNG icons for PWA compatibility (Android/iOS)

package.json

@@ -1,6 +1,6 @@
 {
   "name": "vue-nonograms-solid",
-  "version": "1.12.0",
+  "version": "1.12.1",
   "homepage": "https://nonograms.7u.pl/",
   "type": "module",
   "scripts": {
@@ -20,6 +20,7 @@
     "@vitejs/plugin-vue": "^5.0.4",
     "@vue/test-utils": "^2.4.6",
     "jsdom": "^28.0.0",
+    "sharp": "^0.34.5",
     "vite": "^5.1.4",
     "vite-plugin-pwa": "^0.20.5",
     "vitest": "^4.0.18"