Update README.md with first successful Neural Implicit Representation…

[Zixxy]

… approach

My suggestion is to give Kudos to first successful implementation and paper for Neural Implicit Representation with periodic activation functions.

First it was created in 2018: https://scholar.google.ca/citations?view_op=view_citation&hl=en&user=eWZ79r8AAAAJ&citation_for_view=eWZ79r8AAAAJ:qjMakFHDy7sC

And code: https://github.com/Zixxy/hyperpicture

Then it was refined to paper Hypernetwork functional image representation. That paper predated and motivated authors of "Implicit Neural Rerpresentations with Periodic Activation Functions" to explore discovered phenomena in suggested PR update. Authors have reused representation discovered above and activation functions and rightfully mentioning prior work. I believe this repo should also refer to original authors as well.

Thank you.