Add GitHub action to publish to Hex

.github/workflows/publish-to-hex.yml

@@ -0,0 +1,30 @@
+name: Publish to Hex
+
+on:
+  push:
+    tags:
+      - v*
+
+jobs:
+  publish:
+    name: Publish to Hex
+
+    runs-on: ubuntu-20.04
+
+    steps:
+      - name: Checkout this repository
+        uses: actions/checkout@v3
+
+      - name: Install Erlang and Elixir
+        uses: erlef/setup-beam@v1
+        with:
+          otp-version: "26.0.2"
+          elixir-version: "1.15.4"
+
+      - name: Fetch and compile dependencies
+        run: mix do deps.get + deps.compile
+
+      - name: Publish to Hex
+        run: mix hex.publish --yes
+        env:
+          HEX_API_KEY: ${{ secrets.HEX_API_KEY }}