Add additional resources

[0joshuaolson1]

to the readme, or a separate file? Which are relevant enough to Factoradic?

• comparison of randomness sources
  • by API or browser, no credentials required:
  • https://www.random.org/
  • https://qrng.anu.edu.au/
  • integrated with/provided by hardware (TRNGs?)
  • OSs, PRNGs, hashes/checksums, and why not
  • external hardware? (TRNGs)
  • the issue of trust
• derangement
• bigint library/website recommendation (https://github.com/0joshuaolson1/factoradic/issues/19 <- not very good; I may need to supplement its poor docs) (see usage example linked in last bullet)
• products of factorials
• utilities in issue 25