Worker Secrets API

Hello,

### Context

As a [WordPress](https://wordpress.org/) ops, I use [Simply Static](https://wordpress.org/support/plugin/simply-static/) to deploy some html to CloudFlare Pages.
WordPress allows to add password to pages, I copycat this feature with a [CloudFlare functions ](https://developers.cloudflare.com/pages/platform/functions/) and a basic auth.
At this moment I ignore the passwords set in WordPress and use a single [secret](https://developers.cloudflare.com/pages/platform/functions/bindings/#secrets) for all protected pages.

### Requested feature

I would like to manipulate functions' secrets directly from PHP so every password changes in WordPress could be replicated in CloudFlare.
I need to CRUD over the functions' secrets API.

Thank you a lot

The issue names no repository files or tests; start with the linked Cloudflare Pages Functions and bindings documentation. Done means the PHP library exposes CRUD operations for Pages Functions secrets, with behavior aligned to that API.

Written by the indexing model from the issue text.