Add missing nightlyOf s (#16244)

Please do not merge this before
#16243

Author: bishabosha

docs/_docs/reference/experimental/cc.md

@@ -1,6 +1,7 @@
 ---
 layout: doc-page
 title: "Capture Checking"
+nightlyOf: https://docs.scala-lang.org/scala3/reference/experimental/cc.html
 ---
 
 Capture checking is a research project that modifies the Scala type system to track references to capabilities in values. It is currently

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

@@ -1,6 +1,7 @@
 ---
 layout: doc-page
 title: "MainAnnotation"
+nightlyOf: https://docs.scala-lang.org/scala3/reference/experimental/main-annotation.html
 ---
 
 `MainAnnotation` provides a generic way to define main annotations such as `@main`.

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

@@ -1,6 +1,7 @@
 ---
 layout: doc-page
 title: "Tupled Function"
+nightlyOf: https://docs.scala-lang.org/scala3/reference/experimental/tupled-function.html
 ---
 
 Tupled Function