Fix: catch 404s but ignore time out errors

Author: lwasser

.github/workflows/build-book.yml

@@ -68,4 +68,4 @@ jobs:
           directory: "_build/html"
           arguments: |
             --ignore-files "/.+\/_static\/.+/,/genindex.html/"
-            --ignore-status-codes "404, 403, 429, 503"
+            --ignore-status-codes "0, 403, 429, 503"