Add Authentication section to RTD

[joshuamzm]

Main idea

For auth, it'll be a simple HTTP Authorization header. The value of that header will be Bearer <token>, where you replace \<token> with the string we provide to you. In future releases, we plan to add the ability to rotate the keys and set expiration times too.

Here's an example in curl:

curl -v 'https://api.radiantlabs.co/v1/timelines' \
  -H 'Content-Type: application/json' \
  -H 'Authorization: Bearer <tokenValue>' \
  --data-raw '{"addressFull":"501 RANDALL RD, BALLSTON SPA, NY 12020"}' \
  --compressed