Improved quality of docblock comments

src/Key/KeyInterface.php

@@ -4,6 +4,10 @@ namespace NoccyLabs\Ipc\Key;
 
 interface KeyInterface
 {
+    /**
+     * Get the integer key used for SysV ipc operations
+     *
+     * @return integer
+     */
     public function getKey():int;
-    public function __toString();
 }