change the godbolt link to be this impl instead of a local implementation

[JeffGarland]

The current link in the readme.md points to this: https://godbolt.org/z/5PeKaPWae

which is the original authors link/implementation. The library is now a first class citizen in gobolt so the link should use the beman impl and example -- like this:

https://godbolt.org/z/xMr7vsxE7