Remove and add words, idempontent shuffle

[ConorSheehan1]

1. remove words (slurs)
2. add words (see https://github.com/ConorSheehan1/spelling-bee/issues/1#issue-1345141305)
3. make shuffle idempotent by default
   1. shuffle will keep same pseudo-random order within allAnswers.json files
   2. shuffle will fully shuffle availableLetters by passing Math.random as seed