Option to allow accepting pre-order#88

Would be great to make pre-orders available, perhaps based on stock in transit, or simply just if you allow a product to be sold when out of stock, it changes the buy button to pre-order and add a note with ETA.

Hi folks! This feature has been recently added in v2.10.0, in the form of a new preorder product template.

Docs soon to be updated, but if you need any assistance along the way, please get in touch with us here: https://fluorescent.co/help/contact

Thanks for your patience!