Added first element filter support.

Author: antonLytkin18

src/WS/Utils/Collections/DummyStreamDecorator.php

@@ -63,7 +63,7 @@ public function findAny()
         return $this->decoratedStream->findAny();
     }
 
-    public function findFirst()
+    public function findFirst(callable $filter = null)
     {
         return $this->decoratedStream->findFirst();
     }

src/WS/Utils/Collections/SerialStream.php

@@ -205,11 +205,20 @@ public function findAny()
     /**
      * @inheritDoc
      */
-    public function findFirst()
+    public function findFirst(callable $filter = null)
     {
+        if (!$filter) {
+            /** @noinspection LoopWhichDoesNotLoopInspection */
+            foreach ($this->list as $item) {
+                return $item;
+            }
+            return null;
+        }
         /** @noinspection LoopWhichDoesNotLoopInspection */
         foreach ($this->list as $item) {
-            return $item;
+            if ($filter($item)) {
+                return $item;
+            }
         }
         return null;
     }

src/WS/Utils/Collections/Stream.php

@@ -71,9 +71,10 @@ public function findAny();
 
     /**
      * Returns first collection element or null if absent
+     * @param callable|null $filter
      * @return mixed
      */
-    public function findFirst();
+    public function findFirst(callable $filter = null);
 
     /**
      * Returns last collection element or null if absent