markdown-mode: header-face size & color

[stradicat]

Hierarchical size & color modifications, so that larger, structured markdown files become a bit easier to read, keeping the palette simple.

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• I searched the issue tracker and this hasn't been PRed before.
• My changes are not on the do-not-PR list for this project.
• My changes are visual; I've included before and after screenshots.

• Gruvbox

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• Gruvbox Light

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• Doom-One

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• Doom-One Light

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[hlissner]

I've temporarily converted this to a draft because this PR needs some work. Specifically, I have intentionally avoided adjusting :height's on org and markdown headings. If we're going to add it, I want it standardized behind a variable that's disabled by default, and have it available to all themes.

That said, this is not a request for you to change the PR. The decision rests on some other work that I have brewing for this project. I will get back to this soon.

[stradicat]

Hi @hlissner!

Thanks for considering my PR; no worries, standardization is something I'd do myself for a project like this, with the least amount of friction possible.

Cheers!

[spacefrogg]

For completeness, the meltbus theme has such a variable, doom-meltbus-uniform-font-size, but it is disabled by default (because I like having larger headers, and there was no such discussion when I created it). This being said, I completely support this (also that font heights are uniform by default). So, also take this as a naming suggestion.