Use browser's implementation when this module is loaded by browserify

[ksobue]

When this module is loaded by browserify, use browser's XML implementation instead.

Node module which depends 'xmldom' can run on Node.js and browsers.

[shaqueoneal]

why? do you know browser has web workers?

[emmkimme]

Hi,

could it be possible to prioritize this pull request please.

I would not like to implement another workaround like https://yarnpkg.com/en/package/get-xml or https://github.com/tyrasd/jxon/blob/master/jxon.js to manage browserify.

Thanks