* update highlight.js to latest release v9.13.1
* update to v9.13.1 default.css
does the current default.css include adjustments for the different languages?
* Update highlight.pack.js
* Update readme.tid
* update highlight.pack to 9.15.6
* update version number + included languages
TiddlyWiki passes the MIME type of the tiddler to highlight.js as the
"language brush", but it turns out that highlight.js doesn't actually
understand MIME types. This commit introduces a configuration mapping
between common MIME types and highlight.js language brushes
Fixes#2535