Add GitHub Actions CI to install hugo and build site

.github/workflows/ci.yml

@@ -0,0 +1,39 @@
+name: ci
+on:
+  push:
+    branches:
+      - main
+      - hugo-rewrite
+  pull_request:
+    branches:
+      - main
+
+concurrency:
+  group: ci-${{github.ref}}-${{github.event.pull_request.number || github.run_number}}
+  cancel-in-progress: true
+
+jobs:
+  changes:
+    runs-on: ubuntu-latest
+    permissions:
+      pull-requests: read
+    outputs:
+      publish: ${{ steps.filter.outputs.publish }}
+    steps:
+      - uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # @v2
+        if: ${{ github.event_name == 'push' }}
+        with:
+          fetch-depth: 0
+
+        # For pull requests it's not necessary to checkout the code
+      - uses: dorny/paths-filter@de90cc6fb38fc0963ad72b210f1f284cd68cea36
+        id: filter
+        with:
+          filters: |
+            publish:
+              - '**'
+
+  publish:
+    if: ${{ needs.changes.outputs.publish == 'true' }}
+    needs: changes
+    uses: ./.github/workflows/publish.yml

.github/workflows/publish.yml

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+name: Site Build & Publish
+on:
+  workflow_call:
+
+jobs:
+  build-publish:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683
+    - uses: spack/setup-spack@5ab3c91bdefffffad9a7e45d1d156146afebb3a7
+    - run: |
+        spack mirror add develop https://binaries.spack.io/develop
+        spack buildcache keys --install --trust
+        spack -e . install
+        echo "$(pwd)/.spack-env/view/bin" >> $GITHUB_PATH
+    - run: hugo