Adds doc defining steps to add new catalog in Hub

Signed-off-by: Shivam Mukhade <smukhade@redhat.com>

docs/ADD_NEW_CATALOG.md

@@ -0,0 +1,18 @@
+# Adding New Catalog to Hub
+
+This doc defines the step to add new catalog to Hub. The catalog must follow the structure defined in the [Catalog Organization TEP][tep].
+
+1. Create a pull request to Hub repository and add your catalog details in [Hub Config file][config]. 
+Make sure you give a unique name which is not used for other catalogs defined in Config file.
+    This name will be used in identifying catalog and will be used in API to search resources.
+ eg. `/resource/<catalog-name>/<resource-name>`
+
+2. Once the pull request is merged, Invoke the `/system/config/refresh` API. This will add the new catalog details in db. To access the API, you need to have `config:refresh` scope. 
+
+3. Now, use the Catalog refresh API `catalog/<catalogName>/refresh` to add resources from catalog in hub database. To access the API, you need to have `catalog:refresh` scope.
+    You can check on Hub UI for the new resources.
+
+NOTE: For API documentaton, use `https://api.hub.tekton.dev/schema/swagger.json` in any swagger editor.
+
+[tep]: https://github.com/tektoncd/community/blob/main/teps/0003-tekton-catalog-organization.md
+[config]: https://github.com/tektoncd/hub/blob/d29cf3d2a522bc6d27357083aa0cf896ea22f242/config.yaml#L49