minor #1776 Support dot notation for resources in symfony flex (tomaszhanc)

This PR was merged into the 2.2-dev branch.

Discussion
----------

Support dot notation for resources in symfony flex

Symfony Flex introduced a new notation for routes resources:

```
controllers:
    resource: "../src/Controller"
```

The current implementation of `DirecotryRouteLoader` supports only @ notation to locate a resource by file locator. That PR fix it for Symfony Flex notation.

Commits
-------

ba79b41 Support dot notation for resources in symfony flex

Author: xabbuh

Routing/Loader/DirectoryRouteLoader.php

@@ -37,7 +37,7 @@ public function __construct(FileLocatorInterface $fileLocator, RestRouteProcesso
      */
     public function load($resource, $type = null)
     {
-        if (isset($resource[0]) && '@' === $resource[0]) {
+        if (isset($resource[0]) && in_array($resource[0], ['@', '.'], true)) {
             $resource = $this->fileLocator->locate($resource);
         }
 
@@ -68,7 +68,7 @@ public function supports($resource, $type = null)
             return false;
         }
 
-        if (isset($resource[0]) && '@' === $resource[0]) {
+        if (isset($resource[0]) && in_array($resource[0], ['@', '.'], true)) {
             $resource = $this->fileLocator->locate($resource);
         }