## Duplicate

Sometimes in life, and in learning, it's important to repeat yourself.

Let's use string placeholders to duplicate a string, so that we can make sure we
get our point across.

### Instructions

Declare a variable `duplicate` that repeat the provided variable `sentence`,
separated by a `, ` and add an ` !` at the end.

> so if sentence would be `Hello there`, we expect `Hello there, Hello there !`.
