[Feature] QuickShop PAPI Placeholders

[ItsMicah001]

Describe the Feature
Add placeholders relating to QuickShop that can be used by other plugins through Placeholder API (PAPI).

• %quickshop_customer_sales_value% -Displays the dollar amount of a player's sales made through quickshop. (Selling to another person's shop)
• %quickshop_customer_sales% -Displays how many sales a player has made through quickshop. (Selling to another person's shop)
• %quickshop_sales_value% -Displays the dollar amount of a player's sales made through quickshop. (Sold from their own shop)
• %quickshop_sales% -Displays how many sales a player has made through quickshop. (Sold from their own shop)
• %quickshop_customer_purchased_value% -Displays the dollar amount of a player's purchases made through quickshop. (Buying from another person's shop)
• %quickshop_customer_purchases% -Displays how many purchases a player has made through quickshop. (Buying from another person's shop)
• %quickshop_purchased_value% -Displays the dollar amount of a player's purchases made through quickshop. (Buying with their own shop)
• %quickshop_purchases% -Displays how many purchases a player has made through quickshop. (Buying with their own shop)
• %quickshop_customer_networth% -Displays the net dollar amount of a player's transactions. (Buying and selling to other people's shops)
• %quickshop_networth% -Displays the net dollar amount of a player's transactions. (Buying and selling with their own shops)
• %quickshop_customer_total% -Displays how many transactions a player has made through quickshop. (Through other's shops)
• %quickshop_total% -Displays how many transactions a player has made through quickshop. (Through their own shops)

Screenshots
I cannot think of any applicable screenshots.

Additional context
These placeholders are what I could come up with, however if there are additional placeholders that you may find useful then there may be more to add. PS I am not very good at coming up with names, I hope that the descriptions explain what these placeholders would display.

[RustyDagger]

if all the data needed to get those numbers was available a PAPI extension would not doubt suffice. If its not then i'm not sure if the extension could track/store all that data.
I do like the idea however and its something I would use.

[Ghost-chu]

Pull into TODO list.
Some interface actually will kind of damage performance, i'm pretty sure it won't contains in next version.
BUT, it will in quickshop, this idea is cool and useful, but we need think about how to caching data and how many data need to show.

[sandtechnology]

Pull into TODO list.
Some interface actually will kind of damage performance, i'm pretty sure it won't contains in next version.
BUT, it will in quickshop, this idea is cool and useful, but we need think about how to caching data and how many data need to show.

I think create a github project for all the feature request will be useful for recording todo list, and the implement actually mainly is about data storage and how the data show, just create a new table to store and a new data handler class.