Fix error NU5030: The license file 'LICENSE' does not exist in the pa…

…ckage.

Context https://learn.microsoft.com/en-us/nuget/reference/errors-and-warnings/nu5030#issue

When the filename of the license file has no extension
NuGet reports an error.

```
error NU5030: The license file 'LICENSE' does not exist in the package.
```

Even though we have the `PackagePath` set. According
to the error page, the `PackagePath` in these cases
should be empty.

To fix this we need to split out the `LicenceName` tag into
two values so that they can be set independently. So
we add `LicenceNamePackagePath` tag so that we can do so.
Existing code should behave the same way.

Resources/MonoGame.Library.X.txt

@@ -12,7 +12,7 @@
   </PropertyGroup>
 
   <ItemGroup>
-      <None Include="{LicencePath}" Pack="true" PackagePath="{LicenceName}" />
+      <None Include="{LicencePath}" Pack="true" PackagePath="{LicencePackagePath}" />
   </ItemGroup>
 
   <ItemGroup>

Tasks/PublishPackageTask.cs

@@ -58,11 +58,14 @@ public override async Task RunAsync(BuildContext context)
         projectData = projectData.Replace("{LicencePath}", context.PackContext.LicensePath);
 
         if (context.PackContext.LicensePath.EndsWith(".txt"))
-            projectData = projectData.Replace("{LicenceName}", "LICENSE.txt");
+            projectData = projectData.Replace("{LicenceName}", "LICENSE.txt").Replace ("{LicencePackagePath}", "LICENSE.txt");
         else if (context.PackContext.LicensePath.EndsWith(".md"))
-            projectData = projectData.Replace("{LicenceName}", "LICENSE.md");
+            projectData = projectData.Replace("{LicenceName}", "LICENSE.md").Replace ("{LicencePackagePath}", "LICENSE.md");
+        else if (context.PackContext.LicensePath.EndsWith ("LICENSE"))
+            // https://learn.microsoft.com/en-us/nuget/reference/errors-and-warnings/nu5030#issue
+            projectData = projectData.Replace("{LicenceName}", "LICENSE").Replace ("{LicencePackagePath}", "");
         else
-            projectData = projectData.Replace("{LicenceName}", "LICENSE");
+            projectData = projectData.Replace("{LicenceName}", "LICENSE").Replace ("{LicencePackagePath}", "LICENSE");
 
         var librariesToInclude = from rid in requiredRids from filePath in Directory.GetFiles($"runtimes/{rid}/native")
             select $"<Content Include=\"{filePath}\"><PackagePath>runtimes/{rid}/native</PackagePath></Content>";