Refactor GitHub Actions workflow and add scripts for versioning and release notes extraction

.github/scripts/get_notes.py

@@ -0,0 +1,10 @@
+import os, re
+from pathlib import Path
+
+version = os.environ["VERSION"]
+text = Path("CHANGELOG.md").read_text(encoding="utf-8")
+pattern = rf"(?ms)^##\s+FocusGram\s+{re.escape(version)}\s*$.*?(?=^##\s+|\Z)"
+m = re.search(pattern, text)
+if not m:
+    raise SystemExit(f"Could not find changelog section for version {version}")
+Path("release_notes.md").write_text(m.group(0).strip() + "\n", encoding="utf-8")