fix build_reference.

Author: csyonghe

docs/build_reference.ps1

@@ -9,7 +9,8 @@ Remove-Item -Path ".\stdlib-reference\types" -Recurse -Force
 cd stdlib-reference
 & ../../build/Release/bin/slangc -compile-stdlib -doc
 Move-Item -Path ".\toc.html" -Destination ".\_includes\stdlib-reference-toc.html" -Force
-# git commit -m "Update stdlib reference"
-# git push
+git add .
+git commit -m "Update stdlib reference"
+git push
 cd ../