Rename url_blacklist / url_whitelist

Hello,

Thanks for Cuprite & Ferrum - they're great.

Would the project be open to a contribution towards more inclusive language, specifically renaming:

- `url_blacklist` -> `url_blocklist`
- `url_whitelist` -> `url_allowlist`

Perhaps the old terms could be left as aliases and marked as deprecated until the next major version.

I'd be happy to raise a PR for this.

Cheers,
Oli