highlight search query's stems on search result page

git-svn-id: https://plugins.svn.wordpress.org/instantsearch-for-woocommerce/trunk@1023164 b8457f37-d9ea-0310-8a92-e5e31aec5664
release 1.2.12

git-svn-id: https://plugins.svn.wordpress.org/instantsearch-for-woocommerce/trunk@1023166 b8457f37-d9ea-0310-8a92-e5e31aec5664