Dom reference forces consuming package to use dom lib

This line forces consuming packages to use the dom lib when compiling:
https://github.com/andywer/threads.js/blob/master/src/types/master.ts#L1

This means that the host package can't properly type check for nodejs only. For example, the compiler will not catch if someone tries to use the global `performance` object, which doesn't exist in node.

I believe this is related to https://github.com/andywer/threads.js/issues/418