misc: link to docs (#17)

Author: dated

README.md

@@ -13,7 +13,7 @@
 
 ## Documentation
 
-You can find installation instructions and detailed instructions on how to use this package at the [dedicated documentation site](https://docs.ark.io/developers/sdk/cryptography/php.html).
+You can find installation instructions and detailed instructions on how to use this package at the [dedicated documentation site](https://docs.ark.io/api/sdk/cryptography/php.html).
 
 ## Security