Support additional themes for HTML highlighting

[Prajwal S N]

Currently, the HTML highlighting supports only Solarized Dark, and is hardcoded here:

D-Scanner/src/dscanner/highlighter.d

Line 24 in a958f9a

 html  { background-color: #fdf6e3; color: #002b36; } 

We can provide a --theme flag that allows users to pick from a small predefined set of themes. If anything, it provides an alternative to those who dislike Solarized Dark :P.

Would a PR be accepted for this?

[Jan Jurzitza]

sure, I'm not sure how many people actually use this feature anyway, go wild with PRs.