Note in README.rst on how to run notebooks with the VirtMat kernel

At the moment, running a Jupyter notebook which employs the VirtMat kernel is restricted to the virtmat_kernel/ directory. This means that the notebook file (.ipynb) must be located within the MySampleDirectory/vre-language/virtmat_kernel/ directory. Otherwise the kernel will not be found, resulting in a Jupyter session with a "No kernel" status, and a No module named virtmat_kernel error message in the terminal's log.

It would be useful to add a note about this detail in vre-language/virtmat_kernel/README.rst to ensure currect usability and testing by users.