Basic Dark theme and option for theme in settings

lib/data/appTheme.dart

@@ -0,0 +1,32 @@
+import 'package:flutter/material.dart';
+
+class AppTheme extends ChangeNotifier {
+  ThemeMode _mode = ThemeMode.system;
+  ThemeMode get getMode => _mode;
+
+  void setTheme(ThemeMode newMode) {
+    _mode = newMode;
+    notifyListeners();
+  }
+
+  static ThemeModeDisplay getDisplayOptions(ThemeMode theme) {
+    switch(theme) {
+      case ThemeMode.system:
+        return ThemeModeDisplay(icon: Icons.auto_awesome, displayName: "Systemvorgabe");
+
+      case ThemeMode.light:
+        return ThemeModeDisplay(icon: Icons.dark_mode_outlined, displayName: "Hell");
+
+      case ThemeMode.dark:
+        return ThemeModeDisplay(icon: Icons.dark_mode, displayName: "Dunkel");
+
+    }
+  }
+}
+
+class ThemeModeDisplay {
+  final IconData icon;
+  final String displayName;
+
+  ThemeModeDisplay({required this.icon, required this.displayName});
+}