add typehints and return types

src/Generator/RandomLibAdapter.php

@@ -52,10 +52,10 @@ class RandomLibAdapter implements RandomGeneratorInterface
     /**
      * Generates a string of random binary data of the specified length
      *
-     * @param integer $length The number of bytes of random binary data to generate
-     * @return string A binary string
+     * @param int $length The number of bytes of random binary data to generate
+     * @return string|null A binary string
      */
-    public function generate($length)
+    public function generate(int $length): ?string
     {
         return $this->generator->generate($length);
     }