Add a link to uploading assets in output table

Author: ncipollo

README.md

@@ -48,7 +48,7 @@ This action will create a GitHub release and optionally upload an artifact to it
 |-------------|-----------------------------------------------|
 | id          | The identifier of the created release.        |
 | html_url    | The HTML URL of the release.                  |
-| upload_url  | The URL for uploading assets to the release.  |
+| upload_url  | The URL for uploading assets to the release. See [GitHub's documentation](https://docs.github.com/en/rest/releases/assets?apiVersion=2022-11-28#upload-a-release-asset) for more details. |
 
 ## Example
 This example will create a release when a tag is pushed: