feature #12711 Add documentation for exponential format number (Matthieu Lempereur, MrYamous)

This PR was merged into the 4.4 branch.

Discussion
----------

Add documentation for exponential format number

PR for issue #12537

Adding basic documentation in 4.4 for Exponential format number

Commits
-------

79160c8 Add versionadded in file
7146962 Add documentation for exponential format number

Author: OskarStark

components/expression_language/syntax.rst

@@ -19,6 +19,11 @@ The component supports:
 * **hashes** - using JSON-like notation (e.g. ``{ foo: 'bar' }``)
 * **booleans** - ``true`` and ``false``
 * **null** - ``null``
+* **exponential** - also known as scientific (e.g. ``1.99E+3`` or ``1e-2``)
+
+    .. versionadded:: 4.4
+    
+        The ``exponential`` literal was introduced in Symfony 4.4.
 
 .. caution::