Disable plugin-transform-typeof-symbol in node_modules

Created by: gaearon

I think we should disable this transform: https://www.npmjs.com/package/@babel/plugin-transform-typeof-symbol.

It's very invasive because it touches code that doesn't use new features. Basically it hijacks every typeof. It's guaranteed to make the code slower. And it's not even that useful. It tries to make polyfilled Symbols like native, but I don't think it's that helpful — libraries don't rely on it anyway since most people don't transform node_modules themselves.

Therefore we should disable it.