Adds a new library for code samples

[orta]

Step one in the #120 - creates a library which handles the pre-conversion of a code sample into something which will then be embedded inside code samples.

Basically it takes the new-handbook code sample importer, wraps it with tests via fixtures. Then uses those fixtures as documentation in the README so as it gets built out, there'll be more info.

[orta]

Easy link to the rendered README: https://github.com/microsoft/TypeScript-Website/blob/twoslasher/packages/ts-twoslasher/README.md

[github-actions]

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📖	Deployed to a PR branch - tsconfig old handbook

Got false positives?

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

Typos for README.md

Line	Typo
1	# TypeScript TwoSlasher
4	by the [fourslash test system](https://github.c
13	ndling showing the results of transpilation with certain flags
21	- Think about how to ship to npm
24	The twoslash markup API lives inside your
45	Finally you can set any tsconfig compiler flag using this synt
442	ebug logs by running with the env var of DEBUG="*".
450	is optimized and bundled with Rollup into multiple formats (Common
450	Rollup into multiple formats (CommonJS, UMD, and ES Module).

Lighthouse Scores

/

Performance	Accessibility	Best Practices	SEO	Progressive Web App
0.97	0.9	0.93	0.7	1

/tsconfig

Performance	Accessibility	Best Practices	SEO	Progressive Web App
0.93	0.9	1	0.8	0.96

/docs/handbook/integrating-with-build-tools.html

Performance	Accessibility	Best Practices	SEO	Progressive Web App
0.97	0.9	1	0.77	0.96

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