Add support for the `cf.image` field in `fetch()` properties

[jakubadamw]

Per the definition in https://github.com/cloudflare/workerd/blob/4fb4dbd88d30ff293267680d85a31ddef94fd9b6/types/defines/cf.d.ts#L171-L295.

This is based on the existing https://github.com/cloudflare/workers-rs/pull/233 authored by @seeekr, with some improvements and the completion of the set of properties supported.