add bookmark plugin to readme
add bookmark plugin to readme

st-gwerner/strophejs-plugins,st-gwerner/strophejs-plugins,processone/strophejs-plugins,bluecitymoon/strophejs-plugins,rerobins/strophejs-plugins,adozenlines/strophejs-plugins,adozenlines/strophejs-plugins,processone/strophejs-plugins,rerobins/strophejs-plugins,bluecitymoon/strophejs-plugins