Update/remove lib_examples/base64_example

[critesjosh]

This example is outdated. Update to 1.0.0-beta.6 or remove

[cypriansakwa]

I am working on this. Will be doing pull request soon.

[cypriansakwa]

Hi @critesjosh .

I’ve completed the modernization of the Base64 example to work with Noir 1.0.0-beta.6 and bb 0.84.0.

• The circuit has been updated to follow current Noir best practices (including correct use of public outputs).
• Encoding and decoding correctness is fully verified inside the circuit.
• Additional tests have been added for different inputs, including edge cases.
• Both JavaScript-based and CLI-based proof generation are working as expected.
• The README has been rewritten to reflect the correct setup, usage, and purpose of the example.

👉 All tests pass and the example is now fully functional end-to-end.

Please let me know if I should proceed to open the pull request.

Thanks.