Feature Request: Move getOnrampBuyUrl to separate package for those not using react

### Describe the solution you'd like

The package npm i @coinbase/onchainkit pulls in quite a lot of dependencies, especially for people not using react, graphql & cie (in my case i use angular). It would be great to be able to use utility functions such as getOnrampBuyUrl without needing to pull in that many dependencies, leading to potential conflicts etc...

### Describe alternatives you've considered.

I have resorted to copy and pasting the function getOnrampBuyUrl instead of installing the package.

Locate getOnrampBuyUrl in the @coinbase/onchainkit package and inspect how its current exports pull in React, GraphQL, and other dependencies. Determine the package boundary needed for non-React users, then verify that the utility can be installed and used without those dependencies.

Written by the indexing model from the issue text.