update readme file

[ximlu]

@AndrianBdn @zayass @tulushev @andriydruk @ybiletskyi

Could you please update the README and release a new version? I noticed that the library already supports Swift Toolchain 6.0, but the README and release notes haven't been updated. Many people are unaware that it now supports 6.0.

[andriydruk]

Hi @ximlu, work on Swift 6 in our toolchain is still in progress.
As soon as we finish our testing, we will merge this PR, publish a new version, and update the documentation.
We prioritize stability and want to ensure a reliable release rather than rushing a half-baked solution.