Add CI check for building of documentation and linkcheck

Author: DanielNoord

.github/workflows/checks.yaml

@@ -9,7 +9,7 @@ on:
 
 env:
   # Also change CACHE_VERSION in the other workflows
-  CACHE_VERSION: 5
+  CACHE_VERSION: 6
   DEFAULT_PYTHON: 3.8
   PRE_COMMIT_CACHE: ~/.cache/pre-commit
 
@@ -58,6 +58,7 @@ jobs:
           . venv/bin/activate
           python -m pip install -U pip setuptools wheel
           pip install -U -r requirements_test.txt
+          pip install -U -r doc/requirements.txt
       - name: Generate pre-commit restore key
         id: generate-pre-commit-key
         run: >-
@@ -155,7 +156,7 @@ jobs:
   documentation:
     name: documentation
     runs-on: ubuntu-latest
-    timeout-minutes: 5
+    timeout-minutes: 10
     needs: prepare-base
     steps:
       - name: Check out code from GitHub
@@ -182,3 +183,8 @@ jobs:
         run: |
           . venv/bin/activate
           pytest doc/test_messages_documentation.py
+      - name: Check documentation build and links
+        run: |
+          . venv/bin/activate
+          cd doc
+          make html