Add themes support

[Welding-Torch]

Add support for colorizing output like markdown elements. Like how bat does here:

[davep]

It's not clear what the example is showing (not to me anyway, because "how bat does here" assumes the reader knows what bat is or does). But based on the subject of the issue, this would seem to be more or less a duplicate of #42 perhaps?

The request of the issue is a little more confusing because the above is showing raw markdown, whereas Frogmouth is an application that renders Markdown.

[Welding-Torch]

Sorry about the confusion. The bat tool is an alternative to the cat utility. I included a screenshot of bat above to demonstrate what kind of syntax highlighting I'm looking for. What I mean is: Frogmouth can take inspiration from how bat does syntax highlighting when it prints markdown files. The headings and links are colored. Can frogmouth get something like that?

My suggestion: Add a flag to frogmouth that lets users pick from a selection of pre-defined themes. Eg: frogmouth -t nord or frogmouth -t githubdark. This will change the colors of the rendered markdown elements.

Learn more about bat here: https://github.com/sharkdp/bat

[davep]

So this is about displaying raw Markdown, it seems? Frogmouth isn't a tool for displaying raw Markdown.

[Welding-Torch]

You're misunderstanding. I'm just saying let's have different color schemes in Frogmouth.

So change the color of headings, bold, italics, hyperlinks, etc. through themes.

[davep]

I see; the screenshots you posted were suggesting something else. In that case it looks like this would be served should #42 ever be implemented.