Make sure all the CommonJS modules can be required as normal, rather
than needing to be suffixed with `.default` due to being compiled from
ES modules.
ES modules are the default package export. Commonjs modules are exported
from 'dist/cjs'. Modern bundlers like webpack can consume ES modules.
The addition of the `sideEffects:false` to the `package.json` helps
webpack tree-shaking modules.
Don't rewrite import paths for non-existent modules or types. They will
attempt to be imported from the package's main export. This change
currently requires a module map to be generated for the babel-plugin to
use. The map is automatically regenerated for any commit that alters the
entry file of react-native-web.
Fix#822
