Website: add banner image to be used in the README.
Website: add banner image to be used in the README.

Progress on #216.

scrapp-uk/spfjs,scrapp-uk/spfjs,tchiotludo/spfjs,nicksay/spfjs,theanh/spfjs,theanh/spfjs,youtube/spfjs,youtube/spfjs,tchiotludo/spfjs,youtube/spfjs,theanh/spfjs,theanh/spfjs,tchiotludo/spfjs,tchiotludo/spfjs,scrapp-uk/spfjs,tchiotludo/spfjs,youtube/spfjs,scrapp-uk/spfjs,youtube/spfjs,nicksay/spfjs,nicksay/spfjs,nicksay/spfjs,scrapp-uk/spfjs,theanh/spfjs,nicksay/spfjs