chore: update export conditions

Hello there !
The official runtime export key for cloudflare is `workerd` (not worker).
I believe many apps out there might already be relying on `worker` so I propose to add it alongside it.

Reference : 
- https://developers.cloudflare.com/workers/wrangler/bundling/#conditional-exports

- https://runtime-keys.proposal.wintercg.org/#workerd

package.json

@@ -9,6 +9,7 @@
     "types": "./types/index.d.ts",
     "bun": "./src/index.js",
     "worker": "./cf/src/index.js",
+    "workerd": "./cf/src/index.js",
     "import": "./src/index.js",
     "default": "./cjs/src/index.js"
   },