Fixes codesandbox#2020 - Add missing png extension to manifest icons (codesandbox#2022)

* Add @Jensderond as a contributor

* [BUGFIX][codesandbox#2020] Add missing png extension to icons

Author: Jensderond

.all-contributorsrc

@@ -1261,6 +1261,16 @@
       "contributions": [
         "code"
       ]
+    },
+    {
+      "login": "Jensderond",
+      "name": "Jens de Rond",
+      "avatar_url": "https://avatars2.githubusercontent.com/u/6972822?v=4",
+      "profile": "https://github.com/Jensderond",
+      "contributions": [
+        "bug",
+        "code"
+      ]
     }
   ],
   "repoType": "github",

README.md

@@ -33,12 +33,12 @@
       "sizes": "1024x1024"
     },
     {
-      "src": "apple-touch-icon",
+      "src": "apple-touch-icon.png",
       "type": "image/png",
       "sizes": "57x57"
     },
     {
-      "src": "apple-touch-icon-152x152",
+      "src": "apple-touch-icon-152x152.png",
       "type": "image/png",
       "sizes": "152x152"
     },