Support async properties

[sunkan]

@dcolt

At the moment this isn't supported

class ClassMethods
{
	public TenantId $id {
		get {
			return $this->tenant->id;
		}
	}
}

We are getting these errors

• PSR2.Classes.PropertyDeclaration.Multiple: There must not be more than one property declared per statement
• PSR2.Classes.PropertyDeclaration.ScopeMissing: Visibility must be declared on property "$this"

I don't know how hard it would be to add support for async properties