Fixes #21195: Add more table of contents to pages with longer contents

docs/layout/overview.md

@@ -8,6 +8,11 @@ redirect_from: "/layout/"
 
 Bootstrap includes several components and options for laying out your project, including wrapping containers, a powerful grid system, a flexible media object, and responsive utility classes.
 
+## Contents
+
+* Will be replaced with the ToC, excluding the "Contents" header
+{:toc}
+
 ## Containers
 
 Containers are the most basic layout element in Bootstrap and are **required when using our grid system**. Choose from a responsive, fixed-width container (meaning its `max-width` changes at each breakpoint) or fluid-width (meaning it's `100%` wide all the time).

docs/layout/responsive-utilities.md

@@ -9,6 +9,11 @@ For faster mobile-friendly development, use these utility classes for showing an
 
 Try to use these on a limited basis and avoid creating entirely different versions of the same site. Instead, use them to complement each device's presentation.
 
+## Contents
+
+* Will be replaced with the ToC, excluding the "Contents" header
+{:toc}
+
 ##  Available classes
 
 * The `.hidden-*-up` classes hide the element when the viewport is at the given breakpoint or wider. For example, `.hidden-md-up` hides an element on medium, large, and extra-large viewports.