add IMPORTANT notice that we need to use classic access token. (#24)

Signed-off-by: Tomoya Fujita <Tomoya.Fujita@sony.com>

Author: fujitatomoya

README.md

@@ -34,6 +34,9 @@ ros-ci-for-pr \
 
 Note that the access token must have at least the "public_repo" permission (to be able to post comments), the "gist" permission (to be able to create gists), and the "read:org" permission (to be able to create the Jenkins job).
 
+> [!IMPORTANT]
+> Please use classic access token instead of fine-grained access token. (see [Fine-grained personal access tokens limitations](https://docs.github.com/en/authentication/keeping-your-account-and-data-secure/managing-your-personal-access-tokens#fine-grained-personal-access-tokens-limitations))
+
 ### With a branch name
 
 As an alternative to the above, a branch name can be provided using the `--branch` option.