chore: build packages with lerna

[jobala]

🎉 Thanks for submitting a pull request! 🎉

Summary

Adds a build command for packages in the monorepo and uses lerna to build them. The build command copies src/ to lib/ and doesn't run tsc.

This PR is part of a larger effort -- migrating build to Typescript -- and prepares the ground for incremental migration to Typescript by publishing packages from the lib directory.

---

For us to review and ship your PR efficiently, please perform the following steps:

• [ ] Open a bug/issue before writing your code 🧑‍💻. This ensures we can discuss the changes and get feedback from everyone that should be involved. If you`re fixing a typo or something that`s on fire 🔥 (e.g. incident related), you can skip this step.
• [ ] Read the contribution guidelines 📖. This ensures your code follows our style guide and passes our tests.
• [ ] Update or add tests (if any source code was changed or added) 🧪
• [x] Update or add documentation (if features were changed or added) 📝
• [x] Make sure the status checks below are successful ✅

Fixes #4520