improvement: Colour unification

[sevenseacat]

⚠️ This is branched from #83 - that PR should be reviewed/merged first ⚠️

I noticed that in dark mode, some of the accent colours were orange, and some were a peachy colour, like this:

The orange on the left is using the primary-light colour palette, the peach on the right is using the primary-dark colour palette.

(Personally I prefer the orange, I think it goes better with the Ash logo even though the logo also has the peachy colour in it, but I digress)

This updates a whole bunch of places that were specifying primary-light as default, but not specifying a dark mode variant, most noticeably in the version pills:

And the right-hand nav for modules:

The following may be controversial

Because the dark mode primary colour is a cool peach colour (as opposed to the warm orange colour) I've also updated the code syntax highlighting scheme for dark mode to be a cooler theme.

Before	After

I'm not entirely happy with it still (but I can't seem to find a Pygments version of the One Dark syntax theme anywhere!) but the old version clashed IMO.

(If you don't like it, just let me know and I'll delete the last commit in this branch)

[zachdaniel]

I think it looks 🔥 including the syntax highlighting. I was never really a fan of the existing syntax colors.

[zachdaniel]

Something weird is going on with the build, but its not related to these changes as far as I can tell. My only question is, now that the colors are properly referring to dark mode colors, should we consider changing them to be more orange? If you think that looks better I'm into it :)

[zachdaniel]

🚀 Thank you for your contribution! 🚀