CLI: Rename react template files to jsx

[shilman]

Issue: N/A

What I did

Renamed all JSX files in the react CLI template from .js to .jsx

This is technically more correct, but the primary motivation is to help support community builders (e.g. storybook-builder-vite) whose build systems require .jsx to add JSX support.

How to test

npm init @vitejs/app # choose react
cd vite-project
/path/to/storybook/lib/cli/bin/index.js init --builder storybook-addon-vite

[yannbf]

LGTM!