`@xmldom/xmldom` dependency is not ESM-compatible

[EzraBrooks]

Which means roslibjs 2.0 is currently unusable without a bundler.

I don't think that's a requirement I'm comfortable forcing upon users. I'll find an alternative XML parser for our URDF stuff and shoehorn it in before we ship.

[EzraBrooks]

modifying these APIs would impact ros3djs. Let's do that after 2.0. Short-term solution: make @xmldom/xmldom the only dependency we bundle