docs: document the release process (#17)

Also configure the GitHub auto-generated release notes.

.github/release.yml

@@ -0,0 +1,20 @@
+# see https://docs.github.com/en/repositories/releasing-projects-on-github/automatically-generated-release-notes#configuring-automatically-generated-release-notes
+changelog:
+  exclude:
+    labels:
+      - chore
+      - dependencies
+      - skip-changelog
+  categories:
+    - title: 🎉 New Features
+      labels:
+        - enhancement
+    - title: 🐛 Bug Fixes
+      labels:
+        - bug
+    - title: 📝 Documentation
+      labels:
+        - documentation
+    - title: Other Changes
+      labels:
+        - "*"

README.md

@@ -66,4 +66,19 @@ This project is licensed under the GPL-3.0 license because the backend part of t
 
 The front end part of the code uses the bpmn-visualization library, which is licensed under the Apache-2.0 license. The legends in the project are generated using d3, which is licensed under the ISC license.
 
-Please note that the different licenses may have different requirements, so make sure to review the license terms carefully before using or contributing to this project.
+Please note that the different licenses may have different requirements, so make sure to review the license terms carefully before using or contributing to this project.
+
+## Release how-to
+
+When all updates have been completed, you are ready to publish a new release.
+
+Create a new GitHub release by following the [GitHub help](https://help.github.com/en/github/administering-a-repository/managing-releases-in-a-repository#creating-a-release)
+- for `Tag version`, use a value following the **vX.Y.Z** scheme using the [Semantic Versioning](https://semver.org/).
+- for `Target`
+    - usually, keep the `main` branch except if new commits that you don't want to integrate for the release are already
+      available in the branch
+    - in that case, choose a dedicated commit
+- Description
+    - briefly explain the contents of the new version
+    - make GitHub generates the [release notes automatically](https://docs.github.com/en/repositories/releasing-projects-on-github/automatically-generated-release-notes)
+