Introduced icon for the NuGet packages

For consistency with other projects, the `Icon.png` is placed within the root of the solution, even though it's only needed within the `OnTopic.Data.Transfer` project itself. For now, we're using the Ignia logo as the icon, and have set it to 128x128 per NuGet recommendations.

Author: JeremyCaney

Icon.png

@@ -10,6 +10,7 @@ EndProject
 Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "Solution Items", "Solution Items", "{E838A1C2-B10E-4B70-8939-E1DC47EAFC5B}"
 	ProjectSection(SolutionItems) = preProject
 		GitVersion.yml = GitVersion.yml
+		Icon.png = Icon.png
 		README.md = README.md
 	EndProjectSection
 EndProject

OnTopic.Data.Transfer.sln

@@ -20,8 +20,13 @@
     <NeutralLanguage>en</NeutralLanguage>
     <EmbedUntrackedSources>true</EmbedUntrackedSources>
     <IncludeSymbols>true</IncludeSymbols>
+    <PackageIcon>Icon.png</PackageIcon>
   </PropertyGroup>
 
+  <ItemGroup>
+    <None Include="../Icon.png" Pack="true" PackagePath=""/>
+  </ItemGroup>
+
   <PropertyGroup>
     <PackageProjectUrl>https://github.com/Ignia/Topics-Data-Transfer</PackageProjectUrl>
     <PackageTags>C# .NET CMS DTO</PackageTags>