Migrate from microbundle to tsc to create the module version and use rollup to create the UMD version. Our module build will now not be bundled up but just be ES2017 code using native async/await. It's up to consumers of this package to decide on how to deal with this.
Tests are also run against the transpiled build so we're testing against prod builds.
To make our module build browser compatible, we're now requiring all import specifiers to include .js.
Dropped Object.assign too in favor of ...