async post(value) {
        if (this.value !== value) {
            this.value = value;

            if (value !== null) {
                for (const subscriber of this.subscribers) {
                    await subscriber.onAnchorPost(this);
                }
            }
        }
    }
Post a new value to this anchor and notify all subscribers.
If the value didn't change, no subscriber will be notified

@public
@param {any} value