DB facade alias support (#126)

* Convert DB facade stub method to static

stubs/DBFacade.stubphp

@@ -12,5 +12,5 @@ class DB extends Facade
      *
      * @psalm-taint-sink sql $value
      */
-    public function raw($value) {}
-}
+    public static function raw($value) {}
+}

tests/acceptance/DBFacadeAlias.feature

@@ -0,0 +1,31 @@
+Feature: DB facade alias
+  Want to check that the alias of the DB facade works properly
+
+  Background:
+    Given I have the following config
+      """
+      <?xml version="1.0"?>
+      <psalm totallyTyped="false">
+        <projectFiles>
+          <directory name="."/>
+          <ignoreFiles> <directory name="../../vendor"/> </ignoreFiles>
+        </projectFiles>
+        <plugins>
+          <pluginClass class="Psalm\LaravelPlugin\Plugin"/>
+        </plugins>
+      </psalm>
+      """
+
+  Scenario: call the DB facade alias
+    Given I have the following code
+    """
+    <?php declare(strict_types=1);
+
+    namespace Tests\Psalm\LaravelPlugin\Sandbox;
+
+    function test(): void {
+      \DB::raw(1);
+    }
+    """
+    When I run Psalm
+    Then I see no errors