add a github workflow action to make a release from tags

make a github release for every tag that starts with `v*`,
and a pre-release if the tag contains "-rc".

on the 'systemd/systemd' repo, the "Release" will be draft, so that the
release manager can fill up the notes manually.

on 'systemd/systemd-stable' the release will be created immediately.

info about the action used:
https://github.com/softprops/action-gh-release

.github/workflows/make_release.yml

@@ -0,0 +1,18 @@
+name: Make a Github release
+
+on:
+  push:
+    tags:
+      - "v*"
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v3
+      - name: Release
+        uses: softprops/action-gh-release@v1
+        with:
+          prerelease: ${{ contains(github.ref_name, '-rc') }}
+          draft: ${{ github.repository == 'systemd/systemd' }}