Added net7-target removed unsupported net5

Author: DarthAffe

ScreenCapture.NET/ScreenCapture.NET.csproj

@@ -1,6 +1,6 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
-    <TargetFrameworks>net6.0;net5.0</TargetFrameworks>
+    <TargetFrameworks>net7.0;net6.0</TargetFrameworks>
     <LangVersion>latest</LangVersion>
     <Nullable>enable</Nullable>
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>