Merge pull request #4075 from sharwell/file-scoped-namespaces

Update SA1516 documentation for file-scoped namespaces

Author: sharwell

documentation/SA1516.md

@@ -55,6 +55,8 @@ public event EventHandler SomeEvent
 
 In the example above, the add and remove of the event need to be separated by a blank line because the add is multiline.
 
+When using C# 10 file-scoped namespaces, the `namespace` declaration should be followed by a blank line before any `using`, `extern alias`, or type declarations.
+
 ## How to fix violations
 
 To fix a violation of this rule, add a blank line between the adjacent elements.