minor #11640 Adds the most basic informations about loaders (michaelKaefer)

This PR was submitted for the 4.3 branch but it was squashed and merged into the 3.4 branch instead (closes #11640).

Discussion
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Adds the most basic informations about loaders

I missed this basic informations so I added it :)

Commits
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dcb43b7 Adds the most basic informations about loaders

Author: xabbuh

components/config/resources.rst

@@ -10,6 +10,8 @@ Loading Resources
     :phpfunction:`parse_ini_file` function. Therefore, you can only set
     parameters to string values. To set parameters to other data types
     (e.g. boolean, integer, etc), the other loaders are recommended.
+    
+Loaders populate the application's configuration from different sources like YAML files. The Config component defines the interface for such loaders. The :doc:`Dependency Injection </components/dependency_injection>` and :doc:`Routing </components/routing>` components come with specialized loaders for different file formats.
 
 Locating Resources
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