adds grep package

README.md

@@ -1,10 +1,10 @@
-# ddns
+# ddns (for IPv4)
 
 Dynamic DNS updates for UnitedDomains and Vodafone EasyBox
 
 ## Prerequisites
 ```
-apk add bash bind-tools wget curl libxml2-utils jq
+apk add bash grep bind-tools wget curl libxml2-utils jq
 ```