The value being compared with can be another attribute value
(specified via [[compareAttribute]]) or a constant (specified via
[[compareValue]]. When both are specified, the latter takes
precedence. If neither is specified, the attribute will be compared
with another attribute whose name is by appending "_repeat" to the source
attribute name.
CompareValidator supports different comparison operators, specified
via the [[operator]] property.
The default comparison function is based on string values, which means the values
are compared byte by byte. When comparing numbers, make sure to set the [[$type]]
to [[TYPE_NUMBER]] to enable numeric comparison.