dev: Document how to release

development/release.md

+# Release with Pixi
+
+To create a release with Pixi run the following commands on the **devel** branch:
+
+```bash
+COAL_VERSION=X.Y.Z pixi run release_new_version
+git push origin
+git push origin vX.Y.Z
+git push origin devel:master
+```
+
+Where `X.Y.Z` is the new version.
+Be careful to follow the [Semantic Versioning](https://semver.org/spec/v2.0.0.html) rules.
+
+You will find the following assets:
+- `./build_new_version/coal-X.Y.Z.tar.gz`
+- `./build_new_version/coal-X.Y.Z.tar.gz.sig`
+
+Then, create a new release on [GitHub](https://github.com/coal-library/coal/releases/new) with:
+
+* Tag: vX.Y.Z
+* Title: Coal X.Y.Z
+* Body:
+```
+## What's Changed
+
+CHANGELOG CONTENT
+
+**Full Changelog**: https://github.com/coal-library/coal/compare/vXX.YY.ZZ...vX.Y.Z
+```
+
+Where `XX.YY.ZZ` is the last release version.
+
+Then upload `coal-X.Y.Z.tar.gz` and `coal-X.Y.Z.tar.gz.sig` and publish the release.