docs: update admonition to new GFM specification

This commit updates the README admonitions to the new GFM specification (see https://github.com/orgs/community/discussions/16925#discussioncomment-6506860.

Author: rickstaa

README.md

@@ -7,7 +7,7 @@
 
 Simple (docker-based) GitHub action that can be used to create/update a tag and push it to the remote.
 
-> **Note**
+> [!NOTE]\
 > Since this is a docker-based action and [GitHub currently only supports Linux-based containers](https://docs.github.com/en/actions/creating-actions/creating-a-docker-container-action) running this action on Windows and Mac now needs to be supported (see [#26](https://github.com/rickstaa/action-create-tag/issues/26)).
 
 ## Inputs