Sync doesn't work as expected, value/v-model can get out of sync

If I have the toggle in sync mode connected to a value using v-model (or :value and @input) the toggle can get out of sync of the value.

When sync is selected the toggle function could not set `this.toggled = !this.toggled` directly, but could just send the value through the input event and let the parent's v-model handler set the value.or quickly changes.