Support of QML and HTML Widgets on iOS

It should be technically possible to support QML and HTML widgets in attribute forms on iOS, as QField already demonstrates.

I really don't want to fan a flame here, but it would be nice if you could support something like the following that works in QGIS and QField.

QML Widget:

import QtQuick 2

Loader {
  id: loader
  width:300;height:30
  
  function getJSON(url, callback) {
    var xhr = new XMLHttpRequest();
    xhr.open('GET', url, true);
    xhr.responseType = 'json';
    xhr.onload = function() {
      var status = xhr.status;
      if (status === 200) {
        callback(null, xhr.response);
      } else {
        callback(status, xhr.response);
      }
    };
    xhr.send();
  }

  sourceComponent: Text {
    id: elev
    text: getJSON('https://voibos.rechenraum.com/voibos/voibos?name=hoehenservice&Koordinate='+expression.evaluate("x(transform(@geometry,'EPSG:3857','EPSG:31255'))")+','+expression.evaluate("y(transform(@geometry,'EPSG:3857','EPSG:31255'))")+'&CRS=31255',function(err, data) {if (err == null) { elev.text = data.hoeheDTM.toFixed(2).concat('m'); } else { elev.text = 'Error'}})
  }
}

HTML Widget:

<h1 id="elev"/>
<script>
function getJSON(url, callback) {
    var xhr = new XMLHttpRequest();
    xhr.open('GET', url, true);
    xhr.responseType = 'json';
    xhr.onload = function() {
      var status = xhr.status;
      if (status === 200) {
        callback(null, xhr.response);
      } else {
        callback(status, xhr.response);
      }
    };
    xhr.send();
};
getJSON('https://voibos.rechenraum.com/voibos/voibos?name=hoehenservice&Koordinate='+expression.evaluate("\"x\"")+','+expression.evaluate("\"y\"")+'&CRS=31255',
function(err, data) {
  if (err == null) {
    document.getElementById("elev").innerHTML = data.hoeheDTM.toFixed(2).concat('m');
  }
});
</script>

Start by tracing how attribute-form widgets are handled on iOS, using the QML and HTML examples in the issue and QField as reference. Done means QML and HTML widgets can render and behave in iOS attribute forms with the demonstrated content and appropriate validation or tests.