index.rst: add introduction paragraphs

The homepage of the Yocto Project documentation currently has no
introduction and only displays the table of contents. Inspired by
https://docs.kernel.org, provide a short introduction to the
documentation and also precede each section with a short sentence about
what the section contains.

The section titles are voluntarily duplicated in the document itself and
in the toctree directive, so that the sidebar still contains them, and we
can have text between the section titles and the toctree content.
However this also duplicates the title in the document itself, so add
CSS directive in our customization file to hide the duplicates.

Note that these titles do not show in the PDF and ePub outputs as those
are generated differently.

(From yocto-docs rev: 378360de3dab9b6f349bac852eff645ab0066093)

Signed-off-by: Antonin Godard <antonin.godard@bootlin.com>
(cherry picked from commit 976ee1e250af67b944521b0446c255c88e57db07)
Signed-off-by: Antonin Godard <antonin.godard@bootlin.com>
Signed-off-by: Paul Barker <paul@pbarker.dev>

documentation/index.rst

@@ -5,10 +5,19 @@
    You can adapt this file completely to your liking, but it should at least
    contain the root `toctree` directive.
 
+==========================================
 Welcome to the Yocto Project Documentation
 ==========================================
 
-|
+This is the top level of the Yocto Project documentation tree. The Yocto Project
+documentation is always a work in progress, just like the Yocto Project itself.
+Improvements to the documentation are always welcome; join the
+:yocto_lists:`docs mailing list </g/docs>` if you want to help out.
+
+Introduction and Overview
+=========================
+
+Get started using the Yocto Project.
 
 .. toctree::
    :maxdepth: 1
@@ -20,6 +29,13 @@ Welcome to the Yocto Project Documentation
    Yocto Project Technical Overview <https://www.yoctoproject.org/development/technical-overview/>
    Tips and Tricks Wiki <https://wiki.yoctoproject.org/wiki/TipsAndTricks>
 
+Manuals
+=======
+
+A collection of manuals covering many aspects of the Yocto Project, including
+reference definitions, tutorials, and details about the project's
+infrastructure.
+
 .. toctree::
    :maxdepth: 1
    :caption: Manuals
@@ -36,9 +52,14 @@ Welcome to the Yocto Project Documentation
    Test Environment Manual <test-manual/index>
    bitbake
 
+Security Reference
+==================
+
+Security-related processes and contact information for vulnerability reporting.
+
 .. toctree::
    :maxdepth: 1
-   :caption: Security
+   :caption: Security Reference
 
    Yocto Project Security Reference <security-reference/index>
 

documentation/sphinx-static/theme_overrides.css

@@ -103,6 +103,10 @@ em {
     background: #f8f8f8;
 }
 
+section#welcome-to-the-yocto-project-documentation p.caption {
+   display: none;
+}
+
 @media screen {
     .wy-nav-content {
        max-width: 1000px;