Optimize build artifact

[zxqx]

Update our babel-plugin-transform-runtime config to specify exactly which runtime polyfills the library needs.

Currently we're using defaults:

{
  absoluteRuntime: false,
  corejs: false,
  helpers: true,
  regenerator: true,
  useESModules: false
}

We could maybe use babel-plugin-transform-regenerator to more granularly specify runtime transforms.

[zxqx]

We may want to consider one of these two options:

1. Use Promise instead of async/await in useBaseAxios
2. Use something like babel-plugin-transform-async-to-promises to transform async/await to native Promise calls to remove the need for regenerator runtime

Ran a few test builds and it looks like either one of these will reduce the build artifact size by 25-30%.

[therealparmesh]

If we implement #97, I think we would just need to specify a node target in the @babel/preset-env config along with a browserslist entry in package.json and the rest should be taken care of (in theory 😄 ).

[zxqx]

That would be sick - will do a comparison of the current build artifact size vs. the one generated by pika and report back.