feature: add `@IsISO4217` decorator to check currency codes

[bassochette]

Description

validator.js offers validation for currency codes against the ISO4217 standard.

Proposed solution

Implement the @IsIso4217() decorator.

[bassochette]

I'd be glad to implement it and send a PR

[braaar]

Check out the existing validator in validator.js. It's a fairly new addition, so it hasn't been added here yet.

[braaar]

Last time I checked I think I saw that validator.js has been bumped so that 4217 should be available to implement right away, but don't quote me on that 😅

[bassochette]

I saw it in validator.js and needed it today sooooo pull request time ;)