add maskable icons to manifest

https://web.dev/maskable-icon-audit/?utm_source=lighthouse&utm_medium=cli

.lighthouserc.json

@@ -21,10 +21,10 @@
         "uses-optimized-images": "warn",
         "uses-rel-preconnect": "warn",
         "is-crawlable": "off",
+        "modern-image-formats": "off",
         "offscreen-images": "off",
         "uses-long-cache-ttl": "off",
-        "uses-responsive-images": "off",
-        "uses-webp-images": "off"
+        "uses-responsive-images": "off"
       },
       "includePassedAssertions": true
     },

layouts/index.webmanifest

@@ -5,12 +5,26 @@
     {
       "src": "{{ (resources.Get "img/android-chrome-512x512.png").Permalink | safeJS }}",
       "sizes": "512x512",
-      "type": "image/png"
+      "type": "image/png",
+      "purpose": "any"
     },
     {
       "src": "{{ (resources.Get "img/android-chrome-192x192.png").Permalink | safeJS }}",
       "sizes": "192x192",
-      "type": "image/png"
+      "type": "image/png",
+      "purpose": "any"
+    },
+    {
+      "src": "{{ (resources.Get "img/maskable-512x512.png").Permalink | safeJS }}",
+      "sizes": "512x512",
+      "type": "image/png",
+      "purpose": "maskable"
+    },
+    {
+      "src": "{{ (resources.Get "img/maskable-192x192.png").Permalink | safeJS }}",
+      "sizes": "192x192",
+      "type": "image/png",
+      "purpose": "maskable"
     }
   ],
   "start_url": "{{ .Site.BaseURL | safeJS }}",