Reorganize side bar and overview page

Author: odersky

docs/docs/reference/experimental/overview.md

@@ -1,6 +1,6 @@
 ---
 layout: doc-page
-title: "Experimental language features"
+title: "Overview"
 movedTo: https://docs.scala-lang.org/scala3/reference/experimental/overview.html
 ---
 
@@ -15,13 +15,14 @@ They are enabled by importing the feature or using the `-language` compiler flag
 * [`namedTypeArguments`](./named-typeargs.md): Enable support for named type arguments
 * [`saferExceptions`](./canthrow.md): Enable support for checked exceptions.
 
+### Experimental language imports
+
+In general, experimental language features can be imported in an experimental scope (see [experimental definitions](../other-new-features/experimental-defs.md).
+They can be imported at the top-level if all top-level definitions are @experimental.
+
 ### Experimental language features supported by special compiler options
 
 Some experimental language features that are still in research and development can be enabled with special compiler options. These include
 
 * `-Yexplicit-nulls` Enable support for tracking null references in the type system.
 
-### Experimental language imports
-
-In general, experimental language features can be imported in an experimental scope (see [experimental definitions](../other-new-features/experimental-defs.md).
-They can be imported at the top-level if all top-level definitions are @experimental.

docs/sidebar.yml

@@ -114,9 +114,7 @@ sidebar:
           - page: docs/reference/experimental/overview.md
           - page: docs/reference/experimental/canthrow.md
           - page: docs/reference/experimental/erased-defs.md
-          - page: docs/reference/experimental/erased-defs-spec.md
           - page: docs/reference/experimental/named-typeargs.md
-          - page: docs/reference/experimental/named-typeargs-spec.md
           - page: docs/reference/experimental/numeric-literals.md
       - page: docs/reference/syntax.md
       - title: Language Versions