add module badge

README.md

@@ -1,6 +1,7 @@
 # image
 ![tests](https://github.com/nichoth/image/actions/workflows/nodejs.yml/badge.svg)
 [![types](https://img.shields.io/npm/types/@nichoth/image)](README.md)
+[![module](https://img.shields.io/badge/module-ESM%2FCJS-blue)](README.md)
 [![license](https://img.shields.io/badge/license-MIT-brightgreen)](LICENSE)
 
 Create responsive `img` tags, with a `srcset` property that allows browsers to download the best size image. Optionally, create a small, blurry image as a placeholder for the image with the [blur up technique](https://css-tricks.com/the-blur-up-technique-for-loading-background-images/).