✨ Template: Add "Templated from" badge to README.md

Always neat to add a badge, and it makes clear that a package is made/updated with a
template. Ideally, most packages I'm maintaining would have their devops updated via
this template, making it much easier to keep a consisten devops toolset.

Author: mbercx

template/README.md.jinja

@@ -1,3 +1,5 @@
+[![Templated from python-copier](https://img.shields.io/endpoint?url=https://raw.githubusercontent.com/mbercx/python-copier/refs/heads/main/docs/img/badge.json)](https://github.com/mbercx/python-copier)
+
 # `{{package_name}}`
 
 {{description}}