Letter tokenizer

The letter tokenizer breaks text into terms whenever it encounters a character which is not a letter. It does a reasonable job for most European languages, but does a terrible job for some Asian languages, where words are not separated by spaces.

resp = client.indices.analyze(
    tokenizer="letter",
    text="The 2 QUICK Brown-Foxes jumped over the lazy dog's bone.",
)
print(resp)

response = client.indices.analyze(
  body: {
    tokenizer: 'letter',
    text: "The 2 QUICK Brown-Foxes jumped over the lazy dog's bone."
  }
)
puts response

const response = await client.indices.analyze({
  tokenizer: "letter",
  text: "The 2 QUICK Brown-Foxes jumped over the lazy dog's bone.",
});
console.log(response);

POST _analyze
{
  "tokenizer": "letter",
  "text": "The 2 QUICK Brown-Foxes jumped over the lazy dog's bone."
}

The above sentence would produce the following terms:

[ The, QUICK, Brown, Foxes, jumped, over, the, lazy, dog, s, bone ]

The letter tokenizer is not configurable.