Refacto and implementation for new drug

[Pompidup]

• Switching from Javascript to Typescript
• Before refacto I preferred to create a golden master test to make sure that the output was always identical
• Added some script for more facility like yarn test:watch for instant feedback
• Extract drug in abstract class
• Create new class for each drug that extends Drug

I did not look exactly at the time spent performing the exercise, having done it in small sessions over several days I would probably say 3 hours