function equalTo(propertyName, expression, matchCase) {
  return new EqualTo(propertyName, expression, matchCase);
}
Creates a `<PropertyIsEqualTo>` comparison operator.

@param {!string} propertyName Name of the context property to compare.
@param {!(string|number)} expression The value to compare.
@param {boolean} [matchCase] Case-sensitive?
@return {!EqualTo} `<PropertyIsEqualTo>` operator.
@api