Backport changes from stable documentation branch

docs/_docs/reference/experimental/cc.md

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 layout: doc-page
 title: "Capture Checking"
+nightlyOf: https://docs.scala-lang.org/scala3/reference/experimental/cc.html
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 Capture checking is a research project that modifies the Scala type system to track references to capabilities in values. It can be enabled with a `-Ycc` compiler option.

docs/_docs/reference/experimental/main-annotation.md

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 layout: doc-page
 title: "MainAnnotation"
+nightlyOf: https://docs.scala-lang.org/scala3/reference/experimental/main-annotation.html
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 `MainAnnotation` provides a generic way to define main annotations such as `@main`.

docs/_docs/reference/experimental/tupled-function.md

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 layout: doc-page
 title: "Tupled Function"
+nightlyOf: https://docs.scala-lang.org/scala3/reference/experimental/tupled-function.html
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 Tupled Function