Added settings page

lib/services/settings_provider.dart

@@ -0,0 +1,47 @@
+import 'package:flutter/material.dart';
+import 'package:shared_preferences/shared_preferences.dart';
+
+enum ThemeSettings { system, light, dark }
+
+enum ColourSettings { basic, materialYou }
+
+class SettingsProvider with ChangeNotifier {
+  SharedPreferences? prefs;
+
+  String sourceUrl = 'https://github.com/ImranR98/Obtainium';
+
+  // Not done in constructor as we want to be able to await it
+  Future<void> initializeSettings() async {
+    prefs = await SharedPreferences.getInstance();
+    notifyListeners();
+  }
+
+  ThemeSettings get theme {
+    return ThemeSettings
+        .values[prefs?.getInt('theme') ?? ThemeSettings.system.index];
+  }
+
+  set theme(ThemeSettings t) {
+    print(t);
+    prefs?.setInt('theme', t.index);
+    notifyListeners();
+  }
+
+  ColourSettings get colour {
+    return ColourSettings
+        .values[prefs?.getInt('colour') ?? ColourSettings.basic.index];
+  }
+
+  set colour(ColourSettings t) {
+    prefs?.setInt('colour', t.index);
+    notifyListeners();
+  }
+
+  checkAndFlipFirstRun() {
+    bool result = prefs?.getBool('firstRun') ?? true;
+    if (result) {
+      prefs?.setBool('firstRun', false);
+    }
+    return result;
+  }
+}