[LyX/master] Adapt all German and English manuals to new index features

[Juergen Spitzmueller]

commit 0e710626b8b921c527aa1a19932825fdfe232c7f
Author: Juergen Spitzmueller <spitz at lyx.org>
Date:   Wed Nov 2 15:24:13 2022 +0100

    Adapt all German and English manuals to new index features

 lib/doc/EmbeddedObjects.lyx    | 2533 ++++++++++++++++++---
 lib/doc/Math.lyx               | 5014 ++++++++++++++++++++++++++++++++++++----
 lib/doc/de/EmbeddedObjects.lyx | 2356 ++++++++++++++++++--
 lib/doc/de/Math.lyx            | 5020 ++++++++++++++++++++++++++++++++++++----
 4 files changed, 13673 insertions(+), 1250 deletions(-)