Add rule to enforce whitespaces in multiline variables

[xpaczka]

What has been done

This PR introduces a rule that will enforce multline variables to have a whitespace before and after their declaration. The goal of this rule is to improve code readability by adding some breathing space to variables

Before

const x = 0
const y = 1
const object = {
  a: 'some-value'
  b: 'some-value'
}
const z = 2

After

const x = 0
const y = 1

const object = {
  a: 'some-value'
  b: 'some-value'
}

const z = 2