add changelog action

.github/workflows/update-changelog.yml

@@ -0,0 +1,28 @@
+name: "Update Changelog"
+
+on:
+  release:
+    types: [released]
+
+jobs:
+  update:
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v4
+        with:
+          ref: main
+
+      - name: Update Changelog
+        uses: stefanzweifel/changelog-updater-action@v1
+        with:
+          latest-version: ${{ github.event.release.name }}
+          release-notes: ${{ github.event.release.body }}
+
+      - name: Commit updated CHANGELOG
+        uses: stefanzweifel/git-auto-commit-action@v5
+        with:
+          branch: main
+          commit_message: Update CHANGELOG
+          file_pattern: CHANGELOG.md

CHANGELOG.md

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+# Changelog
+
+All notable changes to this project will be documented in this file.
+
+The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/),
+and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
+
+## [Unreleased](https://github.com/mollie/mollie-api-php/compare/v3.0.0...HEAD)