[TODO] Remove transpiling from node / browser testing

[matthew-dean]

Tools like Vite can run just find without needing to "transpile" module code into CommonJS just for testing. Even browser builds could support module-based testing, as this would be supported by Chromium

Blocked by

• [TODO] Set up a standard test runner - remove some custom test code #42

Sub-tasks

• Remove transpilation from builds
• Make sure tests are executing for all Node environments
• Make sure tests are executing for browser-based testing