feat(pwa) update mask icon

Make it a 512 square and specify its purpose as just "maskable" since this can't
go anywhere.

static/pwa/manifest.json

@@ -22,9 +22,9 @@
     },
     {
       "src": "icons/iconMask.png",
-      "sizes": "196x196",
+      "sizes": "512x512",
       "type": "image/png",
-      "purpose": "any maskable"
+      "purpose": "maskable"
     }
   ],
   "start_url": "/",

twa/twa-manifest.json

@@ -13,14 +13,10 @@
   "enableNotifications": false,
   "startUrl": "/",
   "iconUrl": "https://meet.jit.si/static/pwa/icons/icon512.png",
+  "maskableIconUrl": "https://meet.jit.si/static/pwa/icons/iconMask.png",
   "splashScreenFadeOutDuration": 300,
-  "signingKey": {
-    "path": "./jitsi-upload.keystore",
-    "alias": "upload"
-  },
   "appVersionName": "20.5.0",
-  "appVersionCode": 3,
-  "shortcuts": [],
+  "appVersionCode": 1,
   "generatorApp": "bubblewrap-cli",
   "webManifestUrl": "https://meet.jit.si/static/pwa/manifest.json",
   "fallbackType": "customtabs",