[mod] engine gitea: compatible with modern gitea or forgejo

Without this patch the Gitea Search Engine is only partially compatible with
modern gitea or forgejo:

- Fixing some JSON Fields
- Using Repository Avatar when Available

To Verify My results you can look at the Modern API doc and results, its
available on all Gitea and Forgejo instance by Default.  Heres an Search API
result of Mine:

- https://git.euph.dev/api/v1/repos/search?q=ccna

searx/engines/gitea.py

@@ -1,7 +1,8 @@
 # SPDX-License-Identifier: AGPL-3.0-or-later
-"""Engine to search in collaborative software platforms based on Gitea_.
+"""Engine to search in collaborative software platforms based on Gitea_ or Forgejo_.
 
 .. _Gitea: https://about.gitea.com/
+.. _Forgejo: https://forgejo.org/
 
 Configuration
 =============
@@ -23,6 +24,11 @@ Optional settings are:
     base_url: https://gitea.com
     shortcut: gitea
 
+  - name: forgejo.com
+    engine: gitea
+    base_url: https://code.forgejo.org
+    shortcut: forgejo
+
 If you would like to use additional instances, just configure new engines in the
 :ref:`settings <settings engine>` and set the ``base_url``.
 
@@ -95,13 +101,14 @@ def response(resp):
                 'url': item.get('html_url'),
                 'title': item.get('full_name'),
                 'content': ' / '.join(content),
-                'img_src': item.get('owner', {}).get('avatar_url'),
+                # Use Repository Avatar and fall back to Owner Avatar if not set.
+                'thumbnail': item.get('avatar_url') or item.get('owner', {}).get('avatar_url'),
                 'package_name': item.get('name'),
-                'maintainer': item.get('owner', {}).get('login'),
+                'maintainer': item.get('owner', {}).get('username'),
                 'publishedDate': parser.parse(item.get("updated_at") or item.get("created_at")),
                 'tags': item.get('topics', []),
-                'popularity': item.get('stargazers_count'),
+                'popularity': item.get('stars_count'),
-                'homepage': item.get('homepage'),
+                'homepage': item.get('website'),
                 'source_code_url': item.get('clone_url'),
             }
         )