feat(build): don't run ci on site update commit

Author: kt3k

update.sh

@@ -5,5 +5,5 @@ git clone -b master https://github.com/nodejsjp/nodejsjp.github.com.git build
 npm run build
 cd build
 git add .
-git commit -m 'chore(site): update build'
+git commit -m 'chore(site): update build [skip ci]'
 git push origin HEAD