Improve composer meta information

- Add link to documentation
- Mark non feature branches

Signed-off-by: Michal Čihař <michal@cihar.com>

composer.json

@@ -15,9 +15,11 @@
     "support": {
         "forum": "https://www.phpmyadmin.net/support/",
         "issues": "https://github.com/phpmyadmin/phpmyadmin/issues",
-        "wiki": "http://wiki.phpmyadmin.net/",
+        "wiki": "https://wiki.phpmyadmin.net/",
+        "docs": "https://docs.phpmyadmin.net/",
         "source": "https://github.com/phpmyadmin/phpmyadmin"
     },
+    "non-feature-branches": ["RELEASE_.*"],
     "require": {
         "php": ">=5.5.0"
     },