[gimp-web] content: improve introduction.

[Jehan <jehanp src gnome org>]

commit 5e31e80d3723d02d668f96827039afc8c99d1932
Author: Jehan <jehan girinstud io>
Date:   Fri Jun 3 15:12:49 2022 +0200

    content: improve introduction.
    
    - Add a "summary" which will be used as 'description' and
      'og:description' metadata (otherwise it just uses the first few words
      in the page).
    - Make a small intro, rather than starting directly with the outdated
      warning message.
    - Fix a bit the text.

 content/books/index.md | 17 ++++++++++-------
 1 file changed, 10 insertions(+), 7 deletions(-)
---
diff --git a/content/books/index.md b/content/books/index.md
index 73164ba1..c4851fd0 100644
--- a/content/books/index.md
+++ b/content/books/index.md
@@ -1,18 +1,21 @@
 Title: Books About GIMP
 Date: 2015-08-14T13:58:40-05:00
 Author: Pat David
+Summary: Non-exhaustive list of published books about GIMP
 Status: hidden
 
-⚠️ *This page is outdated; we are missing many books published the last
-few years. If you wish to add a book about GIMP to this list, please
-[contribute modifications to this
-file](https://gitlab.gnome.org/Infrastructure/gimp-web/-/blob/testing/content/books/index.md).*
+This page is a non-exhaustive list of published books about GIMP, as
+reported by the community.
 
-*The file format is *markdown* (you may also look and copy the syntax
+🛈 These books are not endorsed by the GIMP project. We simply list what
+we are notified of.
+
+⚠️ *We are missing many books published the last few years. To add a book
+to this list, please [contribute
+modifications](https://gitlab.gnome.org/Infrastructure/gimp-web/-/blob/testing/content/books/index.md).
+<br/>The file format is *markdown* (you may also look and copy the syntax
 used for listing other books). Keep the order by publication date.* ⚠️
 
-🛈 These books are not endorsed by the GIMP project. We simply list what
-exists when we are notified.
 
 ## Blanco y Negro con GIMP (2 ed.) (Español / Spanish)