Chiu's cubic Ramanujan graphs

[Fe-r-oz]

Explicit constructions of Ramanujan graphs include the Cayley-type graphs of Lubotzky–Phillips–Sarnak (1988), Chiu’s construction (1992), and Morgenstern’s construction (1994). We already support the LPS construction implemented in #6 and Morgenstern Ramanujan graphs. Implement the Chiu's Ramanujan graphs from reference. Reference on explicit constructions: https://arxiv.org/pdf/2003.11673