[doc] add options section

README.md

@@ -29,6 +29,11 @@ asset name, you can specify the wanted asset by adding a pipe symbol and the fil
 ]
 ````
 
+## options
+### targets: string[] - required
+These are the asset names in which you want the placeholders to be replaced.
+
+## examples
 Let's assume, our service worker has the following content
 
 ````