Changelog.md should state that PR #1459 is a breaking change

[j-ac]

My system does not have the opus libraries, and updating from 0.37 -> 0.38 began causing my project to crash on an unwrap().

Result::unwrap()` on an `Err` value: "OPUS support not available"

This holds up under a minimal example:

/// Executes on 0.37, but unwraps an error on 0.38 on systems missing codecs
fn main() {
    mixer::init(mixer::InitFlag::all()).unwrap();
}

This is almost certainly caused by PR #1459 which is not currently marked as a breaking change

[antonilol]

This is expected behavior, there was a logic bug that may have caused init to not return an error even when a library could not be found.
I updated the changelog to correctly mark this as a breaking change, see #1514