Add support for railpack.json (SchemaStore#5136)

- Register Railpack schema in catalog with railpack.json file pattern
- Point to external schema hosted at https://schema.railpack.com

Railpack is a deployment tool that uses railpack.json for build and deploy configuration.
The schema is maintained by Railpack at https://schema.railpack.com
Reference: https://railpack.com/config/file/

Co-authored-by: Claude <[email protected]>

Author: iloveitaly

src/api/json/catalog.json

@@ -4997,6 +4997,12 @@
       "fileMatch": ["railway.toml", "railway.json"],
       "url": "https://railway.com/railway.schema.json"
     },
+    {
+      "name": "Railpack",
+      "description": "Configuration file for Railpack deployment tool",
+      "fileMatch": ["railpack.json"],
+      "url": "https://schema.railpack.com"
+    },
     {
       "name": "Rattler-build",
       "description": "Rattler-build recipe",