Add jsxPragmaFrag support to typescript transform

[JLHwung]

Q	A
Fixed Issues?	Resolves #11935
Minor: New Feature?	Yes
Tests Added + Pass?	Yes
Documentation PR Link	babel/website#1945
Any Dependency Changes?
License	MIT

This PR adds support for jsxPragmaFrag so that preset-typescript does not elide Fragment imports like import { Fragment } from "preact".

Prior work: #9317, unfortunately that PR was abandoned due to lack of upstream support at that time. /cc @Tarnadas, the author of #9317.

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Sandbox	Source
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[babel-bot]

Build successful! You can test your changes in the REPL here: https://babeljs.io/repl/build/27256/

[JLHwung]

This change is invisible to users since (jsxPragmaFrag).split(".")[0] still returns React. It is meant to align with

babel/packages/babel-plugin-transform-react-jsx/src/transform-classic.js

Lines 6 to 9 in df9ee2c

	const DEFAULT = {
	pragma: "React.createElement",
	pragmaFrag: "React.Fragment",
	};

[calebeby]

Hi! Is there a blocker for merge or is this ready to go?