Typescript init: suggest jsx: "react" in tsconfig

[itsMapleLeaf]

Transpilation is done by Babel, which ignores the tsconfig, so this setting (or any tsconfig setting) doesn't affect compilation, only type checking.

Setting it to react raises a type error if react is not imported, and gives a quick fix to import react. The linter rule does not give a quick fix.

I've set it to suggest the value react instead of forcing it, because people might need to set it to something else in their project for whatever reason.

Verified that it works by cloning create-react-app from master, installing the local versions, and using it to compile a personal project. Setting "jsx": "react" does not affect the build size or content.

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[ianschmitz]

Thanks @kingdaro. This is a good improvement.