Update documentation regarding #6

Author: willemstuursma

README.md

@@ -118,6 +118,9 @@ $mutex->synchronized(function () use ($bankAccount, $amount) {
 });
 ```
 
+Timeouts are supported as an optional second argument. This uses the pcntl extension if 
+possible or busy waiting if not.  
+
 #### MemcachedMutex
 
 The **MemcachedMutex**

composer.json

@@ -44,6 +44,9 @@
         "predis/predis": "~1.0",
         "squizlabs/php_codesniffer": "^3.2"
     },
+    "suggest": {
+      "ext-pnctl": "Enables locking with flock without busy waiting in CLI scripts"
+    },
     "archive": {
         "exclude": ["/tests"]
     },