Because you can't place javascript inside github readme files. Please go to the Project Page to grab the button and demo.
Pull requests are happily accepted. Please make the pull request to the upstream branch, and not Master. Also, please create a Github Issue explaining the issue and the change. Thanks.
Smartling Tags Checker Works in all major modern browsers. Meaning, I have not tested IE. But it should work in 9+. People have been reporting issues with all bookmarklets in IE11. smh...