Add license links to remaining JS files

[jacob-willden]

Of the 5 scripts optionally used in Redlib, 2 of them are marked with licenses that make them LibreJS compatible:

1. hls.min.js
2. playHLSVideo.js

This pull request adds license links for LibreJS to the remaining 3 scripts:

1. check_update.js
2. copy.js
3. highlighted.js