Fix NOTE in README (#500)

Probably the most exciting PR you've seen (in your lives?).

Related to fun I was having over in
- UCL-ARC/research-software-practices#30

Author: samcunliffe

README.md

@@ -15,7 +15,8 @@ repo, and we welcome questions there or in the `#helpme` channel on the
 🍪 Our template is a [cookiecutter] template which automatically creates new
 Python packages with our recommended tooling set up and ready to go.
 
-> **Note** If you're making a package within a community that has an existing
+> [!NOTE]
+> If you're making a package within a community that has an existing
 > package template (e.g., [`scikit-hep`](https://github.com/scikit-hep/cookie)),
 > we recommend using their template instead of this one.