deploy latest docs to github pages (#3606)

inspired by https://bsky.app/profile/zachdaniel.dev/post/3lea2llgvcc2j

.github/workflows/docs.yml

@@ -0,0 +1,59 @@
+name: Docs
+
+on:
+  push:
+    branches:
+      - main
+
+permissions:
+  contents: read
+  pages: write
+  id-token: write
+
+jobs:
+  build:
+    runs-on: ubuntu-22.04
+    env:
+      elixir: 1.18.1
+      otp: 27.2
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Set up Elixir
+        uses: erlef/setup-beam@v1
+        with:
+          elixir-version: ${{ env.elixir }}
+          otp-version: ${{ env.otp }}
+
+      - name: Restore deps and _build cache
+        uses: actions/cache@v4
+        with:
+          path: |
+            deps
+            _build
+          key: ${{ runner.os }}-mix-${{ env.elixir }}-${{ env.otp }}-${{ hashFiles('**/mix.lock') }}-docs
+          restore-keys: |
+            ${{ runner.os }}-mix-${{ env.elixir }}-${{ env.otp }}-
+      - name: Install Dependencies
+        run: mix deps.get --only docs
+
+      - name: Build docs
+        run: mix docs
+
+      - name: Upload artifact
+        uses: actions/upload-pages-artifact@v2
+        with:
+          path: doc/
+
+  # Deployment job
+  deploy:
+    environment:
+      name: github-pages
+      url: ${{steps.deployment.outputs.page_url}}
+    runs-on: ubuntu-latest
+    needs: build
+    steps:
+      - name: Deploy to GitHub Pages
+        id: deployment
+        uses: actions/deploy-pages@v2