feat: publish unlisted GTIN tool

site/gtin/manifest.webmanifest

@@ -0,0 +1,34 @@
+{
+  "name": "GTIN Generator",
+  "short_name": "GTIN",
+  "description": "Artikelnummer eingeben, GTIN erzeugen und den EAN-Barcode direkt vom Bildschirm scannen – offline, ohne Anmeldung.",
+  "lang": "de",
+  "dir": "ltr",
+  "start_url": "./",
+  "scope": "./",
+  "display": "standalone",
+  "orientation": "any",
+  "background_color": "#ffffff",
+  "theme_color": "#ffffff",
+  "categories": ["business", "productivity", "utilities"],
+  "icons": [
+    {
+      "src": "./icons/icon-192.png",
+      "sizes": "192x192",
+      "type": "image/png",
+      "purpose": "any"
+    },
+    {
+      "src": "./icons/icon-512.png",
+      "sizes": "512x512",
+      "type": "image/png",
+      "purpose": "any"
+    },
+    {
+      "src": "./icons/icon-maskable-512.png",
+      "sizes": "512x512",
+      "type": "image/png",
+      "purpose": "maskable"
+    }
+  ]
+}