Update readme

readme.md

@@ -47,6 +47,12 @@ Example responses:
 `{"session":"some_session_id","result":true}`
 `{"session":"some_session_id","result":false,"msg":"Answer incorrect."}`
 
+###Content-Security-Policy and Nonces
+
+Add `data-stylenonce="nonce_here"` to the `.captcheck_container` div.
+If you have multiple CAPTCHAs on one page, only one of them needs the nonce
+specified.
+
 
 Installation
 ------------