add change log.

.gitea/workflows/release.yaml

@@ -26,9 +26,15 @@ jobs:
       - run: cmake -S . -B build
       - run: cmake --build build --target all
       - run: build/Bilby
+      - name: Generate Changelog
+        run: |
+          current_tag=$(git describe --tags --abbrev=0)
+          previous_tag=$(git describe --tags --abbrev=0 ${current_tag}^)
+          git log ${previous_tag}..${current_tag} --reverse --pretty=format:"%s" | nl -w2 -s". " > ${{ github.workspace }}-CHANGELOG.txt
       - name: Upload Gitea Release
         uses: akkuman/gitea-release-action@v1
         with:
+          body_path: ${{ github.workspace }}-CHANGELOG.txt
           files: |-
             build/Bilby