Revisit the targeted platforms

[Jericho]

StrongGrid currently targets net48, netstandard2.1, net60 and net7.0. Net 6.0 when out-of-support earlier this summer and Net 7.0 will reach end-of-support in about a month from now so I was about to suggest dropping these two frameworks and adding Net 9.0 which should be released momentarily.

But I started second-guessing my choice of targets mainly because StrongGrid does not depend on features that are specific to any of these net platforms, so why target them specifically? Wouldn't it be enough to simply target net48 and netstandard2.1?