Update CLI docs to list new tokenizers

[dmarx]

This sort of thing, but sprinkled over a variety of parts of the codebase.

gpt_bpe/cmd/tokens_transformer/tokens_transformer.go

Lines 13 to 16 in 5340876

	inputTokenizerId := flag.String("input_tokenizer", "gpt2",
	"input tokenizer id [gpt2, pile, clip, huggingface-id]")
	outputTokenizerId := flag.String("output_tokenizer", "gpt2",
	"output tokenizer id [gpt2, pile, clip, huggingface-id]")

Tokenizers to add:

gpt_bpe/gpt_bpe.go

Lines 112 to 114 in 5340876

	const VOCAB_ID_LLAMA = "llama-tokenizer"
	const VOCAB_ID_LLAMA_3 = "llama3-tokenizer"
	const VOCAB_ID_MISTRAL = "mistral-tokenizer"

Which I believe internally use the identifiers llama, llama3, and mistral respectively.