function createDropdown(key, options) {
    return m(
        "select",
        {
            value: this.settings[key],
            onchange: (e) => {
                this.settings[key] = e.target.value;
                this.saveEnabled = true;
            },
        },
        options
    );
}
Generates vnode for a dropdown setting

@since 3.3.1

@param string key     Settings key
@param array options  Array of objects with value and text fields
@return Vnode