Scratch Package Refactor Countdown List

[pmalacho-mit]

• [ ] Fix 'watch' mode (Rollup seems to not be rebuilding when a change is made)
• [ ] Add jsdoc's to tagged tempalte
• [ ] Update templates to use tagged template
• [ ] Update extensions README to use tagged template: https://github.com/mitmedialab/prg-extension-boilerplate/blob/dev/extensions/README.md
• [ ] Attempt fresh install of repo (@pmalacho-mit can do this if @mayarajan3 is memory constrained) and confirm setup is documented well enough -- this actually might already be done
• [ ] ...

https://github.com/mitmedialab/prg-extension-boilerplate/pull/348