minor #18060 [String] Mention FrenchInflector and Interface (MrYamous)

This PR was submitted for the 6.2 branch but it was merged into the 5.4 branch instead.

Discussion
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[String] Mention FrenchInflector and Interface

Mention FrenchInflector 🐓

Commits
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d173ef3 mention french inflector and interface in String doc

Author: javiereguiluz

components/string.rst

@@ -649,6 +649,12 @@ class to convert English words from/to singular/plural with confidence::
 The value returned by both methods is always an array because sometimes it's not
 possible to determine a unique singular/plural form for the given word.
 
+.. note::
+
+    Symfony also provide a :class:`Symfony\\Component\\String\\Inflector\\FrenchInflector`
+    and an :class:`Symfony\\Component\\String\\Inflector\\InflectorInterface` to implements
+    if you need to use your own inflector.
+
 .. _`ASCII`: https://en.wikipedia.org/wiki/ASCII
 .. _`Unicode`: https://en.wikipedia.org/wiki/Unicode
 .. _`Code points`: https://en.wikipedia.org/wiki/Code_point