[CI] document release workflow

Author: olivierdalang

.github/workflows/release.yaml

@@ -4,12 +4,12 @@ on:
   push:
     branches:
       - master
-      - release-**
   pull_request:
     branches:
-      - '**'
+      - master
   release:
-    types: [published]
+    types:
+      - published
 
 jobs:
 

README.md

@@ -14,3 +14,8 @@ Code style is enforced with pre-commit. To use :
 pip install pre-commit
 pre-commit install
 ```
+
+releases
+--------
+
+To make realeses, create a github release with tag name of format `vX.Y.Z` (optionally `vX.Y.Z-R`)