[TASK] Improve ViewHelper documentation

* Add examples to ViewHelpers that did not have any example yet.
* Add cross references between ViewHelpers where a different ViewHelper
  was mentioned.
* Add full stop to end if sentences.
* Fix indentation within examples.
* Add some syntax like code.
* Fix escaping of PHP classes with namespaces by wrapping them with
  :php:`` text role.
* Use https for urls to php.net.
* Remove '/en/' path from urls to php.net. This ensures the current user
  language is auto detected. Not forcing anyone to keep english.

Relates: #88600
Releases: master, 9.5
Change-Id: I2394890a20adba06719fa35990044057346dfb2b
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/61104


Tested-by: TYPO3com <noreply@typo3.com>
Tested-by: Daniel Goerz <daniel.goerz@posteo.de>
Tested-by: Tymoteusz Motylewski <t.motylewski@gmail.com>
Reviewed-by: Daniel Goerz <daniel.goerz@posteo.de>
Reviewed-by: Tymoteusz Motylewski <t.motylewski@gmail.com>