Section deprecation guidance

[Speedcup]

Summary

• Added SwiftUI Section initializer guidance to clarify that Section("Title") { ... } remains current.
• Documented the renamed positional header/footer initializers and the preferred Section { } header: { } footer: { } replacement.

Sources

• https://developer.apple.com/documentation/swiftui/section/init(header:content:)
• https://developer.apple.com/documentation/swiftui/section/init(footer:content:)
• https://developer.apple.com/documentation/swiftui/section/init(header:footer:content:)

[AvdLee]

Thanks for your contribution @Speedcup!