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builder.RootComponents.Add<HeadOutlet>("head::after");
When the ::after pseudo-selector is specified,
the contents of the root component are appended
to the existing head contents instead of replacing
the content. This allows the app to retain static
head content in wwwroot/index.html without having
to repeat the content in the app's Razor components.
In Simple words - Enable Us To Modify Html Head Metadatas