Jli/ts amount in given out

[throwbackjams]

Main components:

• Add method on Market class to calculate the amount of units in given a desired amount of units out
• Add Mocha testing library (+ mocha types and Chai, which is used for asserts in Mocha)
• Write unit test on the above function using Mocha
• Fix outdate docs on the getMarketExpectedOutAmount utility function