feat(github): twitter username at user screen

lib/screens/gh_user.dart

@@ -145,6 +145,14 @@ class _User extends StatelessWidget {
                   launchStringUrl(url);
                 },
               ),
+            if (p.twitterUsername != null)
+              AntListItem(
+                prefix: const Icon(Ionicons.logo_twitter),
+                child: Text('@${p.twitterUsername!}'),
+                onClick: () {
+                  launchStringUrl('https://twitter.com/${p.twitterUsername}');
+                },
+              ),
           ],
         ),
         CommonStyle.verticalGap,

packages/gql_github/lib/user.graphql

@@ -30,6 +30,7 @@ fragment UserParts on User {
   url
   email
   websiteUrl
+  twitterUsername
   viewerCanFollow # TODO: remove in viewer query
   viewerIsFollowing
   sponsors {