Fix to the readme.md

[Z30G0D]

This example won't work unless either is performed:

• Sending the streamlit an explicit path to the function (or it always try to launch the script from the temporary folder following a rendering.

or

• Defining a the repo's root in `threejs_renderer_st.ThreejsRenderer(path='.')

[Z30G0D]

@Tanneguydv