Upgrade to dotnet 6, and update

[nick-gravgaard]

I wanted to have a go at doing the dojo, but I noticed the code is currently using dotnet 5 which reached its end-of-support date last week (10th of May). I thought I'd be a good citizen and have a go at upgrading it to dotnet 6. As part of this I also needed to update the version numbers in dotnet-tools.json, and I also opted to bring over some improvements that have been made upstream by copying bits from the files generated by "dotnet new SAFE".