Refactor release script to be more modular

.github/workflow_data/release.py

@@ -0,0 +1,19 @@
+#!/usr/bin/env python
+import json
+import os
+
+if __name__ == "__main__":
+    notes_path = '.github/workflow_data/release.md'
+    with open(os.environ['GITHUB_EVENT_PATH']) as f:
+        changelog = json.load(f.read())['pull_request']['body']
+    with open(notes_path, "r") as f:
+        template = f.read()
+    notes = template.format(
+        ARTIFACT_TGZ=os.environ['ARTIFACT_TGZ'],
+        ARTIFACT_WEB=os.environ['ARTIFACT_WEB'],
+        ARTIFACT_ZIP=os.environ['ARTIFACT_ZIP'],
+        VERSION_TAG=os.environ['VERSION_TAG'],
+        CHANGELOG=changelog
+    )
+    with open(notes_path, "w") as f:
+        f.write(notes)