Support RockChat 4.x up

according to field object form https://developer.rocket.chat/reference/api/rest-api/endpoints/team-collaboration-endpoints/chat-endpoints/postmessage#attachment-field-objects .
fill information properly.

gitea-rocketchat.hooks.js

@@ -100,9 +100,10 @@ const giteaEvents = {
         for (var i = 0; i < commits.length; i++) {
             var commit = commits[i];
             var shortID = commit.id.substring(0, 7);
-            output = '[#' + shortID + '](' + commit.url + '): \n' + commit.message
             attachment.fields.push({
-                value: output,
+                short: false,
+                title: '[#' + shortID + '](' + commit.url + '): \n',
+                value: commit.message,
             });
         }