Adding OpenHaystack Mobile app

Co-Authored-By: Lukas Burg <lukas.burg@hemalu.de>

openhaystack-mobile/lib/deployment/hyperlink.dart

@@ -0,0 +1,31 @@
+import 'package:flutter/material.dart';
+import 'package:url_launcher/url_launcher.dart';
+
+class Hyperlink extends StatelessWidget {
+  /// The target url to open.
+  String target;
+  /// The display text of the hyperlink. Default is [target].
+  String _text;
+
+  /// Displays a hyperlink that can be opened by a tap.
+  Hyperlink({
+    Key? key,
+    required this.target,
+    text,
+  }) : _text = text ?? target, super(key: key);
+
+  @override
+  Widget build(BuildContext context) {
+    return InkWell(
+      child: Text(_text,
+        style: const TextStyle(
+          color: Colors.blue,
+          decoration: TextDecoration.underline,
+        ),
+      ),
+      onTap: () {
+        launch(target);
+      },
+    );
+  }
+}