Add the ability for multiple alert sounds depending on what product is found to be in stock

[jaw20]

Referencing #1242 .

Seems like this would be a good idea to help improve and distinguish what exactly is being alerted for.

(It's also a quality of life feature for people who stream streetmerchant.)

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Description

Implement a way for a user to specify specific mp3s to play when specific products come in stock rather than having the ability to only play one notification sound for all products

Possible solution

Modify playSound to take a link variable (which would be passed from sendNotification ), with playSound being able to have a condition for if a specific sound as been specified for a product in .env. And if it has, take the custom link. This could be implemented the same way the phone numbers match with carriers, in order to allow for a custom amount of links and specific products.