Run server on localhost and check that

The link checker treats some internal links as external,
    and treats those relative paths as absolote, resulting errors, ie:

URL        `/theme/img/3rd/registry_logo.svg'
Name       `DataLad-Registry'
Parent URL file:///home/austin/devel/centerforopenneuroscience.org/output/projects.html, line 153, col 9
Real URL   file:///theme/img/3rd/registry_logo.svg
Check time 0.000 seconds
Result     Error: URLError: <urlopen error [Errno 2] No such file or directory: '/theme/img/3rd/registry_logo.svg'>

.github/workflows/check-links.yaml

@@ -18,10 +18,16 @@ jobs:
         run: |
           pip install pelican linkchecker
 
-      - name: Build site
+      - name: Start server
         run: |
-          make html
+          make serve &
+          echo $! > server.pid
+          sleep 1
 
       - name: Check links
         run: |
-          linkchecker -f .linkcheckerrc -t 1 output/
+          linkchecker -f .linkcheckerrc -t 1 https://localhost:8000
+
+      - name: Stop Website Server
+        run: |
+          kill $(cat server.pid)