Fix NuGet Warning NU5048

Icon URL is deprecated in favor of embedding the icon inside the NuGet package.

Oqtane.Server/wwwroot/Themes/Templates/External/Package/[Owner].[Theme].Package.csproj

@@ -1,10 +1,17 @@
-<Project Sdk="Microsoft.NET.Sdk">
+<Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
     <TargetFramework>net5.0</TargetFramework>
     <GeneratePackageOnBuild>false</GeneratePackageOnBuild>
   </PropertyGroup>
-
+  
+  <ItemGroup>
+    <None Include="icon.png">
+      <Pack>True</Pack>
+      <PackagePath></PackagePath>
+    </None>
+  </ItemGroup>
+  
   <ItemGroup>
     <ProjectReference Include="..\Client\[Owner].[Theme].Client.csproj" />
   </ItemGroup>

Oqtane.Server/wwwroot/Themes/Templates/External/Package/[Owner].[Theme].nuspec

@@ -1,4 +1,4 @@
-<?xml version="1.0" encoding="utf-8"?>
+<?xml version="1.0" encoding="utf-8"?>
 <package xmlns="http://schemas.microsoft.com/packaging/2010/07/nuspec.xsd">
   <metadata>
     <id>[Owner].[Theme]</id>
@@ -11,7 +11,7 @@
     <requireLicenseAcceptance>false</requireLicenseAcceptance>
     <license type="expression">MIT</license>
     <projectUrl>https://github.com/oqtane/oqtane.framework</projectUrl>
-    <iconUrl>https://www.oqtane.org/Portals/0/icon.jpg</iconUrl>
+    <icon>icon.png</icon>
     <tags>oqtane module</tags>
     <releaseNotes></releaseNotes>
     <summary></summary>
@@ -22,6 +22,7 @@
   <files>
     <file src="..\Client\bin\Release\net5.0\[Owner].[Theme].Client.Oqtane.dll" target="lib\net5.0" /> 
     <file src="..\Client\bin\Release\net5.0\[Owner].[Theme].Client.Oqtane.pdb" target="lib\net5.0" /> 
-    <file src="..\Client\wwwroot\**\*.*" target="wwwroot" /> 
+    <file src="..\Client\wwwroot\**\*.*" target="wwwroot" />
+    <file src="icon.png" target="" />
   </files>
 </package>