fix: support Gitea 28.0.0 mail templates

tools/data/templates_config.json

@@ -89,7 +89,9 @@
             "HTMLURL": "https://gitea.example.com/repo/project",
             "FullName": "acme/project"
           },
-          "Attachments": []
+          "Attachments": [
+            { "Name": "release-notes.txt", "DownloadURL": "https://gitea.example.com/repo/project/releases/download/v2.0.0/release-notes.txt", "Size": 1536 }
+          ]
         },
         "DisableDownloadSourceArchives": false
       }