feat(sku): support one-time purchase SKUs

[shiftinv]

Summary

https://github.com/discord/discord-api-docs/commit/f0d1615432dada83e34c37972b3d1661735caf59

Adds new SKUTypes and EntitlementTypes, as well as Entitlement.consumed and an Entitlement.consume() method.

Checklist

• [x] If code changes were made, then they have been tested
  • [x] I have updated the documentation to reflect the changes
  • [x] I have formatted the code properly by running pdm lint
  • [x] I have type-checked the code by running pdm pyright
• [ ] This PR fixes an issue
• [x] This PR adds something new (e.g. new method or parameters)
• [ ] This PR is a breaking change (e.g. methods or parameters removed/renamed)
• [ ] This PR is not a code change (e.g. documentation, README, ...)