Upgrade babel and build esm and cjs bundles

[TrySound]

In this diff I suggest to use bundles instead of transpiled with just babel files. There are a few reasons for them

• more controllable size and output
• slightly faster user bundling
• faster browser loading if somebody will use it
• better debugging in development mode without sourcemaps (less webpack stuff)
• hidden internals which may cause breaking changes if user decide to use them

Size snapshot shows also treeshakability for esm bundles so I can apply more optimisation which will be visible to us.

/cc @nkbt @chenglou

[TrySound]

@nkbt Could you merge, so I could start working on further improvements?

[nkbt]

Sure