Add release action

When pushing a tag a release is automatically created

.github/workflows/tag.yaml

@@ -0,0 +1,39 @@
+---
+name: Release
+
+on:  # yamllint disable-line rule:truthy
+  push:
+    tags:
+      - 'v*'
+
+jobs:
+  release:
+    runs-on: "ubuntu-latest"
+    steps:
+      - uses: "actions/checkout@v2"
+      - run: git fetch --unshallow
+
+      - id: changelog
+        run: |
+          curr_tag=$(git describe --tags --abbrev=0)
+          prev_tag=$(git describe --tags --abbrev=0 $curr_tag^)
+          echo "Previous tag: $prev_tag"
+          echo "Current tag: $curr_tag"
+          log="$(git log --format='- %h %s' $prev_tag..$curr_tag)"
+          log="${log//'%'/'%25'}"
+          log="${log//$'\n'/'%0A'}"
+          log="${log//$'\r'/'%0D'}"
+          echo "::set-output name=body::$log"
+
+      - uses: "actions/create-release@v1"
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+        with:
+          tag_name: ${{ github.ref }}
+          release_name: Release ${{ github.ref }}
+          body: |
+            ## Changes
+
+            ${{ steps.changelog.outputs.body }}
+          draft: false
+          prerelease: false