fix: configure Astro site/base and add Pages setup for GitHub Pages deployment

Astro needs site and base config to generate correct asset paths when
hosted at a subpath (google.github.io/scion). Also adds the recommended
configure-pages workflow step.

Author: ptone

.github/workflows/docs.yml

@@ -49,6 +49,10 @@ jobs:
           cache: 'npm'
           cache-dependency-path: docs-site/package-lock.json
 
+      - name: Setup Pages
+        if: github.ref == 'refs/heads/main' && github.event_name != 'pull_request'
+        uses: actions/configure-pages@v5
+
       - name: Install D2
         run: curl -fsSL https://d2lang.com/install.sh | sh -s --
 

docs-site/astro.config.mjs

@@ -21,6 +21,8 @@ import d2 from 'astro-d2';
 
 // https://astro.build/config
 export default defineConfig({
+	site: 'https://google.github.io',
+	base: '/scion',
 	integrations: [
 		d2(),
 		starlight({