Fix #30 build fails with boringssl feature

[samurai00]

In this commit cloudflare/boring@84a80c1 , the X509VerifyResult from cloudflare/boring was modified to Result<(), X509VerifyError> . This change introduces an incompatibility with X509VerifyResult.

Changes in this Pull Request:

This pull request addresses the incompatibility by providing feature-specific code blocks:

• #[cfg(not(feature = "boringssl"))] This block preserves existing behavior for openssl-based stream.ssl().verify_result().
• #[cfg(feature = "boringssl")] Handles the updated boringssl Result<(), X509VerifyError> result type from stream.ssl().verify_result().