minor #19874 Update kernel.rst: Adding example for kernel.project_dir (ThomasLandauer)

This PR was merged into the 6.4 branch.

Discussion
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Update kernel.rst: Adding example for `kernel.project_dir`

Page: https://symfony.com/doc/6.4/reference/configuration/kernel.html#kernel-project-dir

Reason: Showing there is no trailing slash in the path.

Commits
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e116b8a Update kernel.rst: Adding example for `kernel.project_dir`

Author: javiereguiluz

reference/configuration/kernel.rst

@@ -261,12 +261,14 @@ method of the kernel class, which you can override to return a different value.
 ``kernel.project_dir``
 ----------------------
 
-**type**: ``string`` **default**: the directory of the project ``composer.json``
+**type**: ``string`` **default**: the directory of the project's ``composer.json``
 
 This parameter stores the absolute path of the root directory of your Symfony application,
 which is used by applications to perform operations with file paths relative to
 the project's root directory.
 
+Example: `/home/user/my_project`
+
 By default, its value is calculated automatically as the directory where the
 main ``composer.json`` file is stored. This value is also exposed via the
 :method:`Symfony\\Component\\HttpKernel\\Kernel::getProjectDir` method of the