Add a script that fetches specific lnd binaries for each supported
platform/arch into the resources directory and update package scripts
to build for multiple architectures.
Webpack environment `mode` is defined directly in our environment
specific webpack config files. Due to this, we no longer need to
manually set `NODE_ENV` or check to ensure that it has been set.
See:
- https://webpack.js.org/concepts/mode/
Tom Kirkpatrick
Ben Woosley
Jack Mallers
Torkel Rogstad