Add TypeScript Map.groupBy goody

[michaeltmiller]

closes #342

[miorel]

To fix the checks you will need to run yarn package-goodies:test -u in the workspaces/adventure-pack directory. I broke the extraction code at least once before, so this validates that all the goodies can be successfully extracted. It also highlights when changes to the extraction code do or don't impact the resulting goodies output.

[simona1]

Looks good! Thank you for working on it, Michael.

[elimanzo]

hey @michaeltmiller thanks for this PR 💯. I learned a lot about how groupBy works . It reminds me a lot like working with tries, and how we group up prefixes 👍🏽

[miorel]

Thanks for working on it!