Add a --force-colors switch

[The-Compiler]

Thanks for this tool! After hearing about it, I immediately wanted to integrate it with ranger so I can get previews in the file manager.

Unfortunately, rich has no way to force colors (Textualize/rich#343) and disables them with ranger's preview integration because the output isn't a terminal.

Thus, I added a --force-colors switch to get them back:

(it still requires setting COLORTERM=8bit in the environment to get proper 256color support)

[kracekumar]

Thanks for the PR. I came across the problem while developing the tool and decided to add, color support later. I'll merge the PR and make a new release soon.