build: fix user guide localdev script (#247)

Author: Djaytan

docs/user-guide/localdev.sh

@@ -7,4 +7,4 @@ SCRIPT_DIR=$(cd "$(dirname "$0")" > /dev/null 2>&1 && pwd -P)
 echo 'The preview is going to be available at http://localhost:8000/docker-papermc-server/'
 echo
 
-sh "${SCRIPT_DIR}/mkdocs" serve --dev-addr '0.0.0.0:8000'
+sh "${SCRIPT_DIR}/mkdocs.sh" serve --dev-addr '0.0.0.0:8000'