gh: add docs deployment

Based on https://gohugo.io/hosting-and-deployment/hosting-on-github/

.github/workflows/docs.yml

@@ -0,0 +1,69 @@
+---
+name: Docs
+
+on:
+  push:
+    branches:
+      - main
+    paths:
+      - 'docs/**'
+  workflow_dispatch:
+
+permissions:
+  contents: read
+  pages: write
+  id-token: write
+
+concurrency:
+  group: "pages"
+  cancel-in-progress: false
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v3
+
+      - name: Set version env variables
+        run: |
+          cat .version >> $GITHUB_ENV
+
+      - name: Setup Go
+        uses: actions/setup-go@v4
+        with:
+          go-version: "${{env.GO_VERSION}}"
+
+      - name: Install Hugo CLI
+        run: |
+          wget -O ${{ runner.temp }}/hugo.deb https://github.com/gohugoio/hugo/releases/download/v${HUGO_VERSION}/hugo_extended_${HUGO_VERSION}_linux-amd64.deb \
+          && sudo dpkg -i ${{ runner.temp }}/hugo.deb          
+
+      - name: Install Dart Sass
+        run: sudo snap install dart-sass
+
+      - name: Setup Pages
+        id: pages
+        uses: actions/configure-pages@v3
+
+      - name: Install Node.js dependencies
+        run: "[[ -f package-lock.json || -f npm-shrinkwrap.json ]] && npm ci || true"
+
+      - name: Build with Hugo
+        run: make -C docs dist
+
+      - name: Upload artifact
+        uses: actions/upload-pages-artifact@v2
+        with:
+          path: ./docs/public
+
+  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

docs/Makefile

@@ -1,7 +1,10 @@
+.PHONY: install-dependencies
+install-dependencies:
+	brew install hugo
+
 .PHONY: up
 up:
 	@hugo server --minify --disableFastRender
 
-.PHONY: install-dependencies
-install-dependencies:
-	brew install hugo
+dist:
+	@HUGO_ENVIRONMENT=production HUGO_ENV=production hugo --gc --minify