Mark TextualNamespace as @Frozen (#59)

@inlinable public init(_ base: Base) { self.base = base } fails under
-enable-library-evolution because the let property's layout is resilient.
Marking the wrapper struct @Frozen freezes its layout, which is sound for
a transparent single-property wrapper and unlocks library-evolution
consumers (e.g. modules built with BUILD_LIBRARY_FOR_DISTRIBUTION=YES).

Author: axelandersson

Sources/Textual/TextualNamespace.swift

@@ -17,6 +17,7 @@ import Foundation
 ///
 /// SwiftUI views get the namespace through the ``SwiftUICore/View/textual`` property.
 /// Other types can opt into it by conforming to ``TextualCompatible``.
+@frozen
 public struct TextualNamespace<Base> {
   @usableFromInline let base: Base
   @inlinable public init(_ base: Base) { self.base = base }