feat: category / hashtag pages

- with links form stream info
closes #12

lib/widgets/pill.dart

@@ -3,12 +3,18 @@ import 'package:flutter/material.dart';
 class PillWidget extends StatelessWidget {
   final Widget child;
   final Color? color;
+  final void Function()? onTap;
 
-  const PillWidget({super.key, required this.child, required this.color});
+  const PillWidget({
+    super.key,
+    required this.child,
+    required this.color,
+    this.onTap,
+  });
 
   @override
   Widget build(BuildContext context) {
-    return Container(
+    final inner = Container(
       padding: EdgeInsets.symmetric(horizontal: 8, vertical: 4),
       decoration: BoxDecoration(
         borderRadius: BorderRadius.all(Radius.circular(8)),
@@ -16,5 +22,6 @@ class PillWidget extends StatelessWidget {
       ),
       child: child,
     );
+    return onTap != null ? GestureDetector(onTap: onTap, child: inner) : inner;
   }
 }