add 'release' workflow

.github/workflows/create-release.yaml

@@ -0,0 +1,29 @@
+on:
+  push:
+    tags:
+      - 'v*'
+
+name: Create Release
+
+jobs:
+  build:
+    name: Create Release
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v2
+      - name: Check if it is 'NOT RELEASED'
+        shell: bash
+        run: |
+          [[ ! -z $(tail -1 CHANGES.txt | grep -o 'NOT RELEASED\|TENTATIVE') ]] && echo 'NO_RELEASE condition detected! Skip release.' && exit 1 || exit 0
+      - name: Create Release
+        id: create_release
+        uses: actions/create-release@v1
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+        with:
+          tag_name: ${{ github.ref }}
+          release_name: Release ${{ github.ref }}
+          body_path: release.md
+          draft: false
+          prerelease: false

release.md

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+## What's new?
+
+1. TENTATIVE...