Add CI test to ensure that broken docs links are not merged to dev or main

This is the same workflow that gates the publishing of docs to the
website in the publish-technical-documentation-*.yml workflows.

Signed-off-by: Jack Baldry <jack.baldry@grafana.com>

.github/workflows/ci.yml

@@ -26,7 +26,18 @@ jobs:
       - name: Lint All
         run: |
           pre-commit run --all-files
-          
+
+  test-technical-documentation:
+    runs-on: ubuntu-latest
+    steps:
+      - name: "Check out code"
+        uses: "actions/checkout@v3"
+      - name: "Build website"
+        # -e HUGO_REFLINKSERRORLEVEL=ERROR prevents merging broken refs with the downside
+        # that no refs to external content can be used as these refs will not resolve in the
+        # docs-base image.
+        run: |
+          docker run -v ${PWD}/docs/sources:/hugo/content/docs/oncall/latest -e HUGO_REFLINKSERRORLEVEL=ERROR --rm grafana/docs-base:latest /bin/bash -c 'make hugo'
 
   unit-test-backend:
     runs-on: ubuntu-latest