minor #21745 [Routing] Default path for localized routes (javiereguiluz)

This PR was merged into the 6.4 branch.

Discussion
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[Routing] Default path for localized routes

I tried to merge #20218 but it failed, so let's recreate it here.

YAML format is not included because this feature doesn't work (you cannot define an entry without a key or with an empty key).

Commits
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cc251044b [Routing] Default path for localized routes

routing.rst

@@ -2199,6 +2199,9 @@ avoids the need for duplicating routes, which also reduces the potential bugs:
             #[Route(path: [
                 'en' => '/about-us',
                 'nl' => '/over-ons'
+                // optionally, you can define a path without a locale. It will be used
+                // for any locale that does not match the locales above
+                '/about-us',
             ], name: 'about_us')]
             public function about(): Response
             {
@@ -2240,6 +2243,9 @@ avoids the need for duplicating routes, which also reduces the potential bugs:
             $routes->add('about_us', [
                 'en' => '/about-us',
                 'nl' => '/over-ons',
+                // optionally, you can define a path without a locale. It will be used
+                // for any locale that does not match the locales above
+                '/about-us',
             ])
                 ->controller([CompanyController::class, 'about'])
             ;