Massive overhaul

- The project was restarted using Android Studio.
- Adoptive platform-specific widgets has been removed due to build issues with Android.
- Dual-licensed under the BSD-3-Clause license and UNLICENSE.

.vscode/tasks.json

@@ -45,6 +45,13 @@
       "args": ["pub", "upgrade"],
       "problemMatcher": [],
       "label": "flutter: flutter pub upgrade"
+    },
+    {
+      "type": "flutter",
+      "command": "flutter",
+      "args": ["pub", "outdated"],
+      "problemMatcher": [],
+      "label": "flutter: flutter pub outdated"
     }
   ]
 }