Add "readonly" option

[fcfangcc]

Sometimes we don't allow user to edit it. readonly will be necessary.

<cron-light v-model="value" @error="error=$event" readonly></cron-light>

[abichinger]

Thank you for this suggestion. I'll definitely add that

[abichinger]

This feature is available in @vue-js-cron/light@^3.1.0 🎉
I called the option disabled