[Docs] Add a page on error handling

[Daenyth]

• Include an example of the most common errors that you'd get
  • Incorrect types being most common
• Screenshots of what the error output looks like (even if only to have as an easily-linked selling point)
• A section on any built-in error combinators (like how doobie has attemptSomeSql and so on)
• A tiny overview of the common cats methods that you'd use (especially since cats lacks in-depth error handling docs)