Add build scripts to generate source maps

[jar-stripe]

Why?

When debugging into the Stripe SDK from a project or script, it can be useful to have the JS source maps so that you can step into and inspect the original Typescript source. This PR adds build scripts into package.json to build the cjs and esm packages with source maps.

What?

• added build-dev, build-esm-dev, and build-cjs-dev yarn build scripts; these are mirrors of build, build-esm, and build-cjs that also pass --sourceMap true to tsc