Rewrite ReadMe

[dario-coscia]

Hi all! With the 0.2 becoming the new release I think we should update the readme file:

Why?

• We have introduced many new things at package level, so now PINA is no longer only for PINNs but also NO, ROMs and SciML at large
• Code of conduct and security should be added
• Maybe adding a section with people using our work (to show reliability)
• Too many emojis imho

[FilippoOlivo]

Hi all! With the 0.2 becoming the new release I think we should update the readme file:

Why?

• We have introduced many new things at package level, so now PINA is no longer only for PINNs but also NO, ROMs and SciML at large
• Code of conduct and security should be added
• Maybe adding a section with people using our work (to show reliability)
• Too many emojis imho

Thanks @dario-coscia! For sure this is a work that should be done in the near future. Before merging #401 I suggest to modify at least the snippet of the actual README.md file to make it compliant to new version.