Rewrites all links for assets to use a cdn instead. It's not responsible to upload or sync the files anywhere. Some CDNs can do this for you.
Download and install manually or use composer.
You have to enable this filter manually using CDNRewriteRequestFilter.cdn_rewrite config var.
Also define CDNRewriteRequestFilter.cdn_domain with protocol and host.
Your config.yml might look like:
CDNRewriteRequestFilter:
cdn_rewrite: true #global switch
cdn_domain: 'http://cdn.mydomain.com'
rewrite_assets: true #rewrite stuff in assets
rewrite_themes: false #do not rewrite stuff in themes folder