Add support for native TypeScript

[aduth]

Why: One of the other hopes with #5746 was a more direct path to incrementally adopting native TypeScript if we choose. The proposed advantage here is improved syntax, Prettier integration, and clarity of inline code documentation in place of the JSDoc-based typings.

[zachmargolis]

LGTM let's goooo

[aduth]

I need to take a closer look at this logic, which was revised as part of #5746 (not yet deployed to production). Seems like it could already be problematic for .jsx string extraction.

identity-idp/app/javascript/packages/rails-i18n-webpack-plugin/extract-keys-webpack-plugin.js

Lines 44 to 51 in 3945fb0

	/**
	* Given a file name, returns true if the file is a JavaScript file, or false otherwise.
	*
	* @param {string} filename
	*
	* @return {boolean}
	*/
	const isJavaScriptFile = (filename) => filename.endsWith('.js');

Thinking one of either:

• Add more extensions to that list.
• See if there's a better way to detect a Webpack chunk as a script.

[aduth]

I need to take a closer look at this logic, which was revised as part of #5746 (not yet deployed to production). Seems like it could already be problematic for .jsx string extraction.

Actually, it turns out this is fine, likely because it's the output having the .js extension which is important. Confirmed via test case in c7af65b, as well as checking for the string in the modified component:

$ rm -rf public/packs && yarn build && ag -o '"idv.troubleshooting.options.doc_capture_tips"' public/packs
...
public/packs/js/document-capture.es.js
1:"idv.troubleshooting.options.doc_capture_tips"

public/packs/js/document-capture.en.js
1:"idv.troubleshooting.options.doc_capture_tips"

public/packs/js/document-capture.fr.js
1:"idv.troubleshooting.options.doc_capture_tips"