make some projects compatible with netframework4.8 again

Pilz.Win32/Mapped/Keyboard.cs

@@ -1,6 +1,4 @@
-
-using Microsoft.VisualBasic.CompilerServices;
-using Pilz.Win32.Native;
+using Pilz.Win32.Native;
 using Keys = System.Windows.Forms.Keys;
 
 namespace Pilz.Win32.Mapped;
@@ -11,7 +9,7 @@ public class Keyboard
 
     public static bool IsKeyDown(int keyCode)
     {
-        return Conversions.ToDouble(User32.GetKeyState(keyCode).ToString() + 0x8000) < 0d;
+        return Convert.ToDouble(User32.GetKeyState(keyCode).ToString() + 0x8000) < 0d;
     }
 
     public static bool IsKeyDown(Keys keyCode)

Pilz.Win32/NativeTools.cs

@@ -8,8 +8,10 @@ public static class NativeTools
     [Obsolete("Use \"Environment.ProcessPath\" instead.")]
     public static string GetExecutablePath(bool checkRealOS = false)
     {
+#if NET8_0_OR_GREATER
         if (RuntimeInformationsEx.IsOSPlatform(OSType.Windows, checkRealOS))
             return Environment.ProcessPath;
+#endif
         return Process.GetCurrentProcess().MainModule.FileName;
     }
 }

Pilz.Win32/Pilz.Win32.csproj

@@ -1,9 +1,10 @@
 <Project Sdk="Microsoft.NET.Sdk">
   
   <PropertyGroup>
-    <TargetFrameworks>net8.0-windows</TargetFrameworks>
+    <TargetFrameworks>net8.0-windows;netframework4.8</TargetFrameworks>
+    <LangVersion>latest</LangVersion>
     <UseWindowsForms>true</UseWindowsForms>
-    <Version>2.1.0</Version>
+    <Version>2.1.1</Version>
     <ImplicitUsings>enable</ImplicitUsings>
     <Nullable>annotations</Nullable>
   </PropertyGroup>