What doesnt work
I was adding jQuery to a web page. Adding the HTML script tag to the header field doesn’t work within the Website Settings and Web Page (worse: it converts the HTML to text) doctype.
Website settings (doesn’t work)
Web Page (doesn’t work)
Solution
So a workaround was to add it within the Web Page JavaScript field using jQuery.getScript(). I activated caching too in my solution.
$(document).ready(function() {
jQuery.cachedScript = function( url, options ) {
// Allow user to set any option except for dataType, cache, and url
options = $.extend( options || {}, {
dataType: "script",
cache: true,
url: url
});
return jQuery.ajax( options );
};
$.cachedScript( "https://cdnjs.cloudflare.com/ajax/libs/jquery-validate/1.19.3/jquery.validate.min.js" )
.done(function( script, textStatus ) {
console.log( textStatus );
// my code goes here
});
});
Credit to @snv

