Swifterswift: Add more Optional extensions

[omaralbeik]

Add more Optional extensions:

// check if optional is nil or empty collection
public extension Optional where Wrapped: Collection {
    public var isNilOrEmpty: Bool { ... }
}

Here are some unit tests to include to check if you've done this correctly:

func testIsNilOrEmpty() {
   let nilArray: [String]? = nil
   XCTAssertTrue(nilArray.isNilOrEmpty)
   let emptyArray: [String] = []
   XCTAssertTrue(emptyArray.isNilOrEmpty)
   let intArray: [Int] = [1]
   XCTAssertFalse(intArray.isNilOrEmpty)
   let optionalArray: [Int]? = [1]
   XCTAssertFalse(optionalArray.isNilOrEmpty)
}

[SD10]

String is a collection :trollface:

[omaralbeik]

Didn't know Github has a :trollface: emoji 😂