feat: community and custom plugin registries

env.catalog.json

@@ -361,6 +361,11 @@
       "group": "plugins",
       "description": "Use another plugin index instead of the official registry."
     },
+    {
+      "name": "TERMIX_COMMUNITY_REGISTRY_URL",
+      "group": "plugins",
+      "description": "Use another plugin index instead of the community registry. Its plugins still have to be signed with the community key."
+    },
     {
       "name": "TERMIX_PLUGIN_STATS_URL",
       "group": "plugins",