Refactor project file to include package icon and README

- Removed redundant PropertyGroup.
- Added PackageIcon and PackageReadmeFile properties.
- Included image and README in the packaging process.

Author: devlead

src/Spectre.Console.Cli.Extensions.DependencyInjection.png

@@ -2,8 +2,6 @@
 
   <PropertyGroup>
     <TargetFrameworks>netstandard2.0;net9.0;net8.0</TargetFrameworks>
-  </PropertyGroup>
-  <PropertyGroup>
     <PackageId>Spectre.Console.Cli.Extensions.DependencyInjection</PackageId>
     <Authors>achapman,devlead,wcomab</Authors>
     <Copyright>© Alistair Chapman 2018</Copyright>
@@ -13,12 +11,20 @@
     <PackageLicenseExpression>MIT</PackageLicenseExpression>
     <PackageProjectUrl>https://github.com/wcomab/Spectre.Console.Cli.Extensions.DependencyInjection</PackageProjectUrl>
     <GenerateDocumentationFile>true</GenerateDocumentationFile>
+    <PackageIcon>Spectre.Console.Cli.Extensions.DependencyInjection.png</PackageIcon>
+    <PackageReadmeFile>README.md</PackageReadmeFile>
   </PropertyGroup>
+  
   <ItemGroup>
     <PackageReference Include="Microsoft.Extensions.DependencyInjection" Version="8.0.1" Condition="'$(TargetFramework)' == 'netstandard2.0'" />
     <PackageReference Include="Microsoft.Extensions.DependencyInjection" Version="9.0.2" Condition="'$(TargetFramework)' == 'net9.0'" />
     <PackageReference Include="Microsoft.Extensions.DependencyInjection" Version="8.0.1" Condition="'$(TargetFramework)' == 'net8.0'" />
     <PackageReference Include="Spectre.Console.Cli" Version="0.49.1" />
   </ItemGroup>
 
+  <ItemGroup>
+    <None Include="../Spectre.Console.Cli.Extensions.DependencyInjection.png" Pack="true" PackagePath="/" />
+    <None Include="../../README.md" Pack="true" PackagePath="/" />
+  </ItemGroup>
+
 </Project>