Fix future incompatibility

[fgardt]

Marks the extern crate as pub but also hides it from docs.
Resolves the future incompatibility warning from rust-lang/rust#127909.

Fixes #13.

[tisonkun]

cc @GnomedDev I noticed this as well. This PR should be helpful.

[fgardt]

I'm a bit unsure about the msrv check failing, if I try and build on 1.61 with the minimal required dependency versions it works completely fine for me. The dependency versions that are used in the CI msrv check have their own msrv's set at 1.68 (proc-macro2) or 1.71 (quote, unicode-ident).

The ui-test failing seems to be unrelated, opened a separate PR to fix them.

[tisonkun]

I'm a bit unsure about the msrv check failing, if I try and build on 1.61 with the minimal required dependency versions it works completely fine for me. The dependency versions that are used in the CI msrv check have their own msrv's set at 1.68 (proc-macro2) or 1.71 (quote, unicode-ident).

Yes, prior to Rust Edition 2024, these compatible versions would all be upgraded to the latest version. For Edition 2024, it will check the Rust version; if that field exists, it will select a compatible version.

In the current situation, if I remember correctly regarding MSRV (Minimum Supported Rust Version), you need to run Cargo Update and then change it to that exact MSRV-compatible version.

See https://github.com/apache/opendal/pull/7483/changes as an example.