Re-enable --strict for build

Fixes #764.

We used to have this enabled; it can help catch things like entirely
broken links before they make it into the deployed version.

Author: StevenMaude

justfile

@@ -129,7 +129,7 @@ run: devenv
 
 # Build the documentation
 build: devenv
-    $BIN/mkdocs build
+    $BIN/mkdocs build --strict
 
 # Count words in generated documentation content (within <article> tags)
 wordcount: build