Add wishlist link to FUNDING.yml

[oss-wishlist-bot]

This PR was opened at the request of @emmairwin to add a wishlist link to your repository's sponsor button.

Wishlist: https://oss-wishlist.com/fulfill?issue=140775

This will display the wishlist link in the "Sponsor this project" section of your repository to help wishlist sponsors find and fulfill wishes that help this project.

For more information:

• Open Source Wishlist: https://oss-wishlist.com
• FUNDING.yml settings: https://docs.github.com/en/repositories/managing-your-repositorys-settings-and-features/customizing-your-repository/displaying-a-sponsor-button-in-your-repository