Improve wording of the assembly metadata support

We don't actually retrieve hand-coded attbutes in code, only MSBuild items.

src/ThisAssembly.Metadata/readme.md

@@ -1,19 +1,10 @@
 <!-- include https://github.com/devlooped/.github/raw/main/sponsorlinkr.md -->
 <!-- #metadata -->
 This package provides a static `ThisAssembly.Metadata` class with public 
-constants exposing each `[System.Reflection.AssemblyMetadata(..)]` defined for 
-the project.
+constants exposing each `[System.Reflection.AssemblyMetadata(..)]` defined in 
+the project file as [supported by the .NET SDK](https://learn.microsoft.com/en-us/dotnet/standard/assembly/set-attributes-project-file#set-arbitrary-attributes).
 
-![](https://raw.githubusercontent.com/devlooped/ThisAssembly/main/img/ThisAssembly.Metadata.png)
-
-For an attribute declared (i.e. in *AssemblyInfo.cs*) like:
-
-```csharp
-[assembly: System.Reflection.AssemblyMetadataAttribute("Foo", "Bar")]
-```
-
-A corresponding `ThisAssembly.Metadata.Foo` constant with the value `Bar` is provided. 
-The metadata attribute can alternatively be declared using MSBuild syntax in the project 
+The metadata attribute is declared using MSBuild syntax in the project 
 (for .NET 5.0+ projects that have built-in support for `@(AssemblyMetadata)` items):
 
 ```xml
@@ -22,6 +13,11 @@ The metadata attribute can alternatively be declared using MSBuild syntax in the
   </ItemGroup>
 ```
 
+And a corresponding `ThisAssembly.Metadata.Foo` constant with the value `Bar` is provided 
+for this example.
+
+![](https://raw.githubusercontent.com/devlooped/ThisAssembly/main/img/ThisAssembly.Metadata.png)
+
 <!-- #metadata -->
 <!-- include ../visibility.md -->
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