Support other decorators like underline, background color, etc...

[OmarTawfik]

The vscode-textmate library we use does not just export foreground color, it also supports a bunch of other metadata, like underlines, and background color. We should be able to extract this info and pass it along to the colorization engine.

https://github.com/microsoft/vscode-textmate/blob/9e3c5941668cbfcee5095eaec0e58090fda8f316/src/grammar.ts#L1081-L1099