Feature: #61529 - Add multiple parameter to f:form.checkbox

See forge#61529

Description

Introduce parameter "multiple" for f:form.checkbox ViewHelper.

<f:form action="create" method="POST" name="pizza" object="{pizza}">
        <f:form.checkbox property="covering" multiple="1" value="salami" /><br />
        <f:form.checkbox property="covering" multiple="1" value="ham" /><br />
        <f:form.checkbox property="covering" multiple="1" value="cheese" /><br />
        <f:form.submit value="Send" />
</f:form>

Impact

If you add the parameter "multiple" to your checkboxes, it automatically appends [] to the name of your checkbox.