[BUGFIX] Escape html tags in cshmanual content

Parts of the cshmanual were never shown, because a language variable
contained a <title> tag, that made the browser hide all of the manual
content after that tag.

Resolves: #90675
Releases: master, 9.5
Change-Id: I2d9cf15153f80bd5d0d8ed8cd0864807f30d31f1
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/63607


Tested-by: TYPO3com <noreply@typo3.com>
Tested-by: Georg Ringer <georg.ringer@gmail.com>
Tested-by: Daniel Goerz <daniel.goerz@posteo.de>
Reviewed-by: Georg Ringer <georg.ringer@gmail.com>
Reviewed-by: Daniel Goerz <daniel.goerz@posteo.de>

typo3/sysext/backend/Resources/Private/Partials/ContextSensitiveHelp/Manual.html

 <a id="{manual.table}{f:if(condition:manual.field,then:'.{manual.field}')}"></a>
 
 <h2>{manual.headerLine}</h2>
-<p>{manual.content -> f:format.raw()}</p>
+<p>{manual.content -> f:format.htmlentities() -> f:format.raw()}</p>
 
 <f:if condition="{manual.configuration.details}">
     <h3><f:translate key="LLL:EXT:backend/Resources/Private/Language/locallang_view_help.xlf:details" /></h3>