Improve docs styling and structure

[Blargian]

Placeholder issue for improvements we can make to docs styling and page structure.

Ideas from discussion with Cristina:

• Use titles more effectively
• Use indentation (see BigQuery docs for very effective use of indentation)
• Add white space between sections, even paragraphs
• Style certain elements so that they pop up
• Define a max width of…. 880, test it, see how it goes.
• Increase the line height of regular text to 175%
• Experiment with regular text size 16px (we use 14px)
• get rid of the line rule between sections (makes pages feel like 'boxed' information rather than a narrative)

Examples of documentation with good design that encompass some of the above changes:

https://supabase.com/docs/guides/database/overview
https://vercel.com/docs/observability
https://linear.app/docs/start-guide
https://docs.stripe.com/
https://vuejs.org/guide/introduction.html

[Blargian]

Different elements have different amounts of padding on top and bottom which means that depending on the elements next to each other the spacing can look weird:

Some examples:

e.g. here the header has padding on top and the list on the bottom so there is this stack up effect

e.g. here the gap on top of the code block is more than on the bottom