Adds CSS for markdown tables

[orta]

Fixes #1221 - we used to leave the table styling to be the browser's default, this ended up meh - so I mixed some of the bits I like from GitHub and Microsoft Docs

Before

After

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Also makes the massive CLI options table feel better:

[github-actions]

Got false positives?

Make changes to the global settings spellcheck.json in /artsy/peril-settings.

Typos for JSX.md

Line	Typo
34	corresponding option in your [tsconfig.json](/docs/handbook/tsconfig-json
56	x` files, and is identical in behavior to the angle-bracket type ass
69	element always begins with a lowercase letter, and a value-based ele
69	element always begins with an uppercase letter.
75	However, if this interface is present, then the name of the
304	attributes type_ where child JSXExpressions are taken to be inserted in
333	erride the default type from, eg the [React typings](https://g
333	ault type from, eg the [React typings](https://github.com/Definitel
405	act you should use the [React typings](https://github.com/Definitel
406	These typings define the JSX namespace ap
427	, or an inline @jsx comment pragma to set it on a per-file basis
429	The comment pragma version may be used like so (

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