Purge cache with prefix

Previously a select set of paths were purged due to limitations within
the CloudFlare Account type. This takes advantage of the fact that we
can now purge based upon a path prefix to ensure that all of the docs
will be refreshed.

This will ensure that when the docs are deployed nothing is cached. See https://developers.cloudflare.com/cache/how-to/purge-cache/purge_by_prefix/