Add feature image to toplevel README
Add feature image to toplevel README

eegeo/eegeo-example-app,eegeo/eegeo-example-app,eegeo/eegeo-example-app,eegeo/eegeo-example-app,wrld3d/wrld-example-app,wrld3d/wrld-example-app,wrld3d/wrld-example-app,eegeo/eegeo-example-app,eegeo/eegeo-example-app,wrld3d/wrld-example-app,wrld3d/wrld-example-app,eegeo/eegeo-example-app,wrld3d/wrld-example-app,wrld3d/wrld-example-app,wrld3d/wrld-example-app