Ignore Boolean props in require-default-prop rule

[michalsnik]

This PR addresses #222 by not requiring default key for Boolean props.

I thought about considering the following cases:

{
  a: Boolean,
  b: [Boolean],
  c: {
    type: Boolean,
  },
  d: {
    type: [Boolean],
  }
}

But I'm no longer sure we need to support cases with arrays that contain only Boolean type, and perhaps we should always require default key, when prop type is described by an ArrayExpression 🤔 WDYT @chrisvfritz ?

[chrisvfritz]

While b: [Boolean], is a little strange, it's technically acceptable, so I think it's a good case to cover. I could imagine legitimate reasons for preferring it too. For example, some teams may have a convention of always using the array syntax so that it's clear that multiple types can be added. Or, some prop definitions might be defined programmatically from a schema and these might always use arrays.

[michalsnik]

Oh, now I see I didn't cover d actually. I'll update it @chrisvfritz

[chrisvfritz]

Thanks! 🙂

[znck]

LGTM.