Create doc file for chained controllers (backport #985)

[mergify]

This is an automatic backport of pull request #985 done by Mergify.
Cherry-pick of 185fbea has failed:

On branch mergify/bp/humble/pr-985
Your branch is up to date with 'origin/humble'.

You are currently cherry-picking commit 185fbea.
  (fix conflicts and run "git cherry-pick --continue")
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Changes to be committed:
	new file:   controller_manager/doc/images/chaining_example2.png
	modified:   doc/index.rst

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both added:      controller_manager/doc/controller_chaining.rst

To fix up this pull request, you can check it out locally. See documentation: https://docs.github.com/en/github/collaborating-with-pull-requests/reviewing-changes-in-pull-requests/checking-out-pull-requests-locally

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[christophfroehlich]

This failed because of the backport #1106 of #1104
Which information is correct on humble @destogl?

[christophfroehlich]

thanks, this fixed the sphinx job 🙏