Add "focus" callback event for form fields

[bilalmalkoc]

Is your feature request related to a problem? Please describe.

When focusing on the builder element, dynamically created dom elements can disrupt the functioning of main form if it is in the builder form element. #1077

For example, when we add a button, the select element that changes the "Submit" or "Reset" types of the button disrupts the functioning of the main form because of the name="action" attribute it contains.

Also, if there is no type="button" attribute in the button elements added when focusing, it submits the main form in which the builder is located when clicked.

Describe the solution you'd like

If there is a callback event when focusing on the builder field, we can avoid potential errors by manipulating both the elements inside the field and the properties elements on the right side.

In the callback arguments we must have access to the elements of the form field and the properties elements on the right side.