Implement the automatic update check and installation

lib/consts.dart

@@ -0,0 +1,35 @@
+import 'dart:convert';
+
+import 'package:dio/dio.dart';
+
+class TTConsts {
+  static const UPDATE_URL =
+      "https://git.zontreck.com/AriasCreations/TimeTracker/raw/branch/main/latest-releases.json";
+  static const VERSION = "1.0.0-dev.2";
+  static bool UPDATE_AVAILABLE = false;
+  static UpdateChannel UPDATE_CHANNEL = UpdateChannel.alpha;
+
+  static Future<void> checkUpdate() async {
+    Dio dio = Dio();
+    var reply = await dio.get(UPDATE_URL);
+    var jsData = json.decode(reply.data as String);
+
+    String serverVersion = jsData[UPDATE_CHANNEL.toString()] as String;
+    if (VERSION == serverVersion) {
+      // Up to date
+      UPDATE_AVAILABLE = false;
+    } else
+      UPDATE_AVAILABLE = true;
+  }
+}
+
+enum UpdateChannel {
+  alpha,
+  beta,
+  stable;
+
+  @override
+  String toString() {
+    return name;
+  }
+}