Escape </script> in library JS code for embedding

[izelnakri]

This single line of escaping was needed to be able to embed this string to any html inside <script> tags without having it as a separate js file.

Although the use-case for this is rare, it does happen when I bundle things with esbuild internally and embed the output js string on the fly to the requested html in qunitx, even bundled/transpiled output would preserve the string thus this change was needed.

Otherwise browsers try to close the JS early as it encounters the </script> inside the code which breaks the page/html rendering.

Related stack overflow issue: https://stackoverflow.com/questions/22488830/script-within-a-javascript-string-in-a-script-tag