Allow leading zeros in Kartra phone number fields

<!--
Override Kartra phone number form field validation to allow leading zeros.
Only overrides when field name is "phone", and only works for in-line (non-iframe) opt-in and checkout forms.
Add this code to FOOTER tracking for pages or a custom code block for memberships.
-->
<script>
function newIsValidChar ($el, char, type, rules) {
return ($el[0].name === 'phone' ? !!char.match(/[0-9]/) : oldIsValidChar($el, char, type, rules));
}
function fixIVC (list, obs) {
if (window.isValidChar) {
console.log('fixing isValidChar');
obs.disconnect();
window.oldIsValidChar = window.isValidChar;
window.isValidChar = window.newIsValidChar;
}
}
var bmo = new MutationObserver(fixIVC);
bmo.observe(document.body, { childList: true, subtree: true });
</script>