Mutual TLS now available for Workers

What this post added

Introduced general availability of mTLS support for Cloudflare Workers, enabling Workers to authenticate to services secured by mTLS. This involves uploading client certificates and private keys via `wrangler mtls-certificate upload`, configuring `mtls_certificates` bindings in `wrangler.toml`, and using the `environment.<BINDING>.fetch()` method in Worker code to present the client certificate during the TLS handshake.