Enhancement: More lively syntax highlighting

[pykong]

I like to have a more elaborate syntax highlighting, as such always help comprehensibility. For example, I'd really like to see urls and file links to be of a different color than the remaining text a todo item might be comprised of. Also, nesting depth could be made more obvious by coloring. Like in this rather extreme color theme for JSON: Monokai JSON+

I do not know whether PlainTaks already provides scopes to resolve its different syntax elements or such still need to be implemented. In the former case just adding a default improved color scheme taking full advantage of the whole spectrum of scope would suffice. In the latter case, such scopes would first need to be integrated via a tmLanuage file and still new color schemes provided.

[vovkkk]

URL will be highlighted if it contains scheme and is enclosed within <>

Other kinds of links have no scopes.