minor #1615 [Doc] Clarify collection hydration requirements (gremo)

This PR was merged into the 2.x branch.

Discussion
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[Doc] Clarify collection hydration requirements

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | no <!-- please update src/**/CHANGELOG.md files -->
| Issues        | Fix #1611 <!-- prefix each issue number with "Fix #", no need to create an issue if none exist, explain below instead -->
| License       | MIT

As explained in the related issue, this should help people that doesn't require the full webapp pack, when working with collection of DTOs (otherwise you only get a generic error _Unable to dehydrate value of type "array"_)

Commits
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22a3427 [Doc] Clarify collection hydration requirements

Author: kbond

src/LiveComponent/doc/index.rst

@@ -684,6 +684,12 @@ To work with a collection of DTOs, specify the collection type inside PHPDoc::
         public array $addressDtoCollection;
     }
 
+Collection type extraction from the docblock requires the ``phpdocumentor/reflection-docblock`` library. Make sure it is installed in you application:
+
+.. code-block:: terminal
+
+    $ composer require phpdocumentor/reflection-docblock
+
 Here is how the (de)hydration of DTO objects works:
 
 - All "properties" (public properties or fake properties via