Updating the styles to improve legibility and use BBC Reith typefaces

[JoshTumath]

Is your feature request related to a problem? Please describe.

• The body text is a bit small and the line spacing is a bit tight
• The width of the body is quite wide, so lines of text are quite long, but research shows roughly 60 characters per line is the best for readability.
• It would be nice to add the BBC Reith typefaces

Describe the solution you'd like

• Update the font styles to match GEL guidelines around font styles, which should improve legibility and the reading experience
• Give the body a max-width of 60ch units (falling back to approx ~ 33em units if that's not supported)
• Use black text for headings
• Use Reith Serif for h1 headings and Reith Sans for the rest of the text

I would be happy to submit a PR for this change if the project maintainers are OK with it.

[adamjc]

This sounds like a great idea! I'm all for it

[fuzzyfelt]

We've made some adjustments to the sizing but can't use the Reith font.