Set g:jsx_ext_required = 0 by default

[cloudlena]

Using the .jsx file extension seems outdated and is not used by de facto standards like create-react-app. To me it would therefore make sense to set g:jsx_ext_required = 0 by default.

[trevordmiller]

I agree it would be great to set let g:jsx_ext_required = 0 by default. Almost all JSX projects use .js files.