publish on hex.pm on release creation

.github/workflows/publish_on_release.yml

@@ -0,0 +1,33 @@
+name: Publish release to the Hex.pm
+
+on:
+  release:
+    types: [published]
+
+jobs:
+  publish:
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        otp: ['21.3.8.21']
+        elixir: ['1.8.2', '1.9.4', '1.10.4']
+    steps:
+      - uses: actions/checkout@v2
+      - uses: erlef/setup-elixir@v1
+        with:
+          otp-version: ${{matrix.otp}}
+          elixir-version: ${{matrix.elixir}}
+      - name: Restore dependencies cache
+        uses: actions/cache@v2
+        with:
+          path: deps
+          key: ${{ runner.os }}-mix-${{ hashFiles('**/mix.lock') }}
+          restore-keys: ${{ runner.os }}-mix-
+      - name: Install dependencies
+        run: mix deps.get
+      - name: Run tests
+        run: mix test
+      - name: Publish package
+        run: mix hex.publish --yes
+        env:
+          HEX_API_KEY: ${{ secrets.HEX_API_KEY }}