Use native Base64 APIs for decoding when available

[jonkoops]

Checklist

• I have looked into the Readme and have not found a suitable solution or answer.
• I have searched the issues and have not found a suitable solution or answer.
• I have searched the Auth0 Community forums and have not found a suitable solution or answer.
• I agree to the terms within the Auth0 Code of Conduct.

Describe the problem you'd like to have solved

The proposal for native Base46 APIs that properly handle the Base64URL implementation has reached Stage 3 and has started being implemented in various engines and browsers. This provides an opportunity to use these APIs rather than the custom implementation now present in the package, and could possibly lead to improved performance as well.

Describe the ideal solution

Right now the ideal solution would be to use the built-in API if present and fall back to the custom internal implementation when not supported. Long term the best option would be to drop the internal implementation entirely.

Alternatives and current workarounds

No response

Additional context

No response