docs: Add flag to show notes and usage hints when previewing documentation

Author: euanh

Sources/swift-container-plugin/Empty.swift

@@ -17,3 +17,7 @@
 
 // SwiftContainerPluginDocumentation is an otherwise empty target that includes high-level,
 // user-facing documentation about using the Swift Container Plugin from the command-line.
+
+// To preview the documentation, run the following command:
+//
+// swift package --disable-sandbox preview-documentation --target swift-container-plugin --analyze

Sources/swift-container-plugin/README.md

@@ -6,7 +6,7 @@ user-facing documentation about using the ContainerImageBuilder plugin from the
 To preview the documentation, run the following command:
 
 ```bash
-swift package --disable-sandbox preview-documentation --target swift-container-plugin
+swift package --disable-sandbox preview-documentation --target swift-container-plugin --analyze
 ```
 
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