CI: move docs job into separate workflow

.github/workflows/CI.yml

@@ -56,25 +56,3 @@ jobs:
       - uses: codecov/codecov-action@v5
         with:
           token: ${{ secrets.CODECOV_TOKEN }}
-
-  # The documentation job
-  manual:
-    name: Build manuals
-    runs-on: ubuntu-latest
-
-    steps:
-      - uses: actions/checkout@v5
-      - name: 'Install additional dependencies'
-        run: |
-          sudo apt-get update
-          sudo apt-get install libczmq-dev
-      - uses: gap-actions/setup-gap@v2
-      - uses: gap-actions/build-pkg-docs@v1
-        with:
-          use-latex: 'true'
-      - name: 'Upload documentation'
-        uses: actions/upload-artifact@v4
-        with:
-          name: manual
-          path: ./doc/manual.pdf
-          if-no-files-found: error

.github/workflows/docs.yml

@@ -0,0 +1,35 @@
+name: Docs
+
+# Trigger the workflow on push or pull request
+on:
+  push:
+    branches:
+      - main
+      - master
+  pull_request:
+
+# the `concurrency` settings ensure that not too many CI jobs run in parallel
+concurrency:
+  # group by workflow and ref; the last slightly strange component ensures that for pull
+  # requests, we limit to 1 concurrent job, but for the default repository branch we don't
+  group: ${{ github.workflow }}-${{ github.ref }}-${{ github.ref_name != github.event.repository.default_branch || github.run_number }}
+  # Cancel intermediate builds, but only if it is a pull request build.
+  cancel-in-progress: ${{ startsWith(github.ref, 'refs/pull/') }}
+
+jobs:
+  manual:
+    name: Build manuals
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v5
+      - uses: gap-actions/setup-gap@v3
+      - uses: gap-actions/build-pkg-docs@v2
+        with:
+          use-latex: 'true'
+      - name: 'Upload documentation'
+        uses: actions/upload-artifact@v4
+        with:
+          name: manual
+          path: ./doc/manual.pdf
+          if-no-files-found: error