Add additonnal tip methods, i.e !tip @user 1 beer/shirt/cup/hat

[tzarebczan]

We want to start tipping users LBC so they can purchase merchandise from the LBRY store, so we'd want to be able to do something like: !tip @user 1 shirt. Shirt would just be one example, but it would need to calculate the LBC based on the current price and a fixed USD cost of the merchandise. Is this possible? @jsigwart can help come up with a base list of products which we'll want to support along with the cost (including average shipping costs).

Current swag shop: https://shop.lbry.io/

[nikooo777]

I believe this feature should be implemented together with a refactoring of the bot itself.

When the bot will handle tipping on all platforms together then we should be able to easily add this.

[Eniamza]

@jsigwart Can you list the products please?