Automatically generate and display table on README

[jcohenadad]

The out-of-sync situation between the README and the code https://github.com/shimming-toolbox/tissue-to-MRproperty/blob/main/functions/label.py adds maintenance load and is prone to error.

My suggestion would be to implement a simple github action such that, upon creation of a new release, a CSV with permittivity/conductivity values is generated, and automatically displayed on the README (eg: the README can fetch release assets).

Related to #13 (comment) and #17