Access Object Property Dynamically

Sometimes you don’t know the exact property name when writing code.
In that case, you can use bracket notation to access a property dynamically using a string.
Use the syntax obj[key] instead of obj.key.

Write a function getProp that takes an object and a key (string), and returns the value of the matching property.
Example: getProp({a: 42}, 'a') should return 42.