Added Net6 in the conditional to take the reference System.Drawing.Co…

[luisfbn]

Added Net6 in the conditional to take the reference System.Drawing.Common.
Net35 was removed due to System.Drawing.Bitmap type does not exist on it.

Summary

This PR fixes/implements the following bugs/features:

• .NET 6.0 Compilation Error: The type or namespace name 'QRCode' does not exist in the namespace 'QRCoder'  #382

What existing problem does the pull request solve?**

Creating a .Net 6 Project and try to use QRCode type on it. Visual Studio can't compile due to: The type or namespace name 'QRCode' does not exist in the namespace 'QRCoder'

Closing issues

closes #382

[Briaoeuidhtns]

it isn't available on all net6.0 targets, only the windows one. https://learn.microsoft.com/en-us/dotnet/core/compatibility/core-libraries/6.0/system-drawing-common-windows-only

[codebude]

Hi @luisfbn ,

as @Briaoeuidhtns says - System.Drawing.Common is only available on Windows platforms. That's why I added the restrictions. I don't get how your changes can/shall work. Can you explain it to me? (My understanding is, that this shouldn't be possible.)

[luisfbn]

Hi @codebude
Yes, sorry for the confusion, @Briaoeuidhtns is right.
I only tested on Windows.