Draft: modularise ghc.nix

see https://github.com/alpmestan/ghc.nix/pull/185

.github/workflows/ci.yml

@@ -10,6 +10,11 @@ on:
     paths-ignore:
       - '**/*.md'
 
+permissions:
+  contents: read
+  pages: write
+  id-token: write
+
 jobs:
   build:
     runs-on: ubuntu-latest
@@ -76,6 +81,27 @@ jobs:
       - name: Run nix develop - Test GHC (by running a testsuite subset)
         run: nix develop -Lv --fallback ghc.nix# -c bash -c "hadrian/build -j --flavour=quickest test --test-root-dirs=testsuite/tests/programs"
 
+      - name: Setup pages 
+        id: pages
+        uses: actions/configure-pages@v3
+      - name: build book
+        run: nix build -Lv --fallback ghc.nix#moduleDocs
+      - name: upload-artifact
+        uses: actions/upload-pages-artifact@v2
+        with:
+          path: ./result
+
+  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
+
   cross_compiler_smoketest:
     runs-on: ubuntu-latest