Add Option to cheatsheet

[ashawley]

Give a quick introduction to how Option works, and also show many of the useful methods on Some and None and the equivalent pattern match.

I removed the use of Option from the pattern match section at the begging of the cheatsheet.

Preview:

https://ashawley.github.io/docs.scala-lang/cheatsheets/index.html

The original:

https://docs.scala-lang.org/cheatsheets/index.html

[kotobotov]

some minor improvements

[kotobotov]

do we really need to println something?

[ashawley]

It's not required, but it seems useful to show that the value is no longer an Option. Many of the other examples in the cheatsheet use println.

[Philippus]

maybe add flatten as well?

[ashawley]

I added flatten:

optionOfOption match {
  case Some(Some(x)) => Some(x)
  case _             => None
}