Provide a slog handler

[flimzy]

Summary

Now that log/slog has landed in the standard library, it would be nice to provide an official Sentry handler. There are third-party handlers available (https://github.com/samber/slog-sentry as an example), but having one in this repo that tracks with new features, and corresponds to the existing handlers for other logging systems would make sense to me.

I'm also happy to work on the implementation, if the core team doesn't have the time/resources.

[cleptric]

Closing as a duplicate of #527.

In any case, PRs are always welcome 😃