Update license file to indicate all contributors

[gardners]

Can those not already listed in the license file, but have contributed, please add yourselves, so you get proper recognition?

Thanks,
Paul.

[FeralChild64]

Added my real name - FeralChild64@8307118. I'm afraid only two of us contributed commits so far.

What do you think about adding CREDITS.md, where we could list authors of code snippets/routines we used, authors of important documentation that was helpful, etc.?

[gardners]

Yes, that makes a lot of sense to me to do.