fix: add actual link check step to sphinx_build_link_check.sh

The script was named sphinx_build_link_check and commented as 'Build locally,
and then check links' but only ran the HTML build step. This adds the missing
`sphinx-build -b linkcheck` command to actually check links as intended.

Fixes #284

Author: NucleiAv

docs/scripts/sphinx_build_link_check.sh

@@ -1,5 +1,7 @@
 #!/bin/bash
 # halt script on error
 set -e
-# Build locally, and then check links
-sphinx-build -E -W source build
+# Build the HTML docs
+sphinx-build -E -W source build
+# Check links in the docs
+sphinx-build -b linkcheck source build/linkcheck