ressource registry in file system [wso2 api manager 4.2.0]

Question

I want to create a custom policy in wso2 api manager 4.2.0, and I use this mediator :

I create a xslt file in ../carbon interface and I use this and it works perfectly.

But me I want to use file systems to store xslt and point the xslt mediator to appropriate file, because I want to setup a CI/CD