Move from the Node events module to eventemitter3

[bpierre]

This removes the need for a bundler to polyfill the Node events module in order to use web3-react.

We could also use the events module on npm, but eventemitter3 has a few advantages over it.

[NoahZinsmeister]

in v8, nothing actually extends EventEmitter anymore, just the interface is imported: https://github.com/NoahZinsmeister/web3-react/blob/main/packages/types/src/index.ts#L1

so, hopefully this is a non-issue going forward!