Add pitcms schema (#5342)

Add JSON schema for pitcms, a Git-based headless CMS.
Schema is self-hosted at https://pitcms.net/schema/pitcms.schema.json

Author: yuto343

src/api/json/catalog.json

@@ -9320,6 +9320,12 @@
       "name": "Espanso config.yml",
       "description": "define HOW Espanso acts",
       "url": "https://raw.githubusercontent.com/espanso/espanso/refs/heads/dev/schemas/config.schema.json"
+    },
+    {
+      "name": "pitcms",
+      "description": "Configuration file for pitcms - a Git-based headless CMS",
+      "fileMatch": ["pitcms.json", "pitcms.jsonc"],
+      "url": "https://pitcms.net/schema/pitcms.schema.json"
     }
   ]
 }