Make the lib compatible dotnet standard

[real-felix]

Hi, I like this library, but unfortunately we cannot use it at work since we are developing a net core app and System.Drawing.Image (used by the viewer and the rasterizer) is a Framework API.

Is there a planed port to dotnet standard?

[CanadianHusky]

Hello, If the developers consider making a port to .Net Standard or .Net Core which I have nothing against, please do no neglect or abandon current .Net 4.x path. There are many projects with good old .Net 4, 4.5, 4.6, 4.7, 4.8 etc, with millions of lines of code which work just fine and there is no need to port those to .Net Standart or Core just because Microsoft wants to change their framework far too often. Thanks

[porrey]

I was using this on NET5 and created a pull request with my updates. This provides support for

netstandard2.1;netcoreapp3.1;net5.0;net4;net461;net47;net471;net472

[CrapuleJack]

We also got stuck on the need for this to be standard / core compatible, please make it happen good sir.