Migrate API (etc) docs to syncstorage-rs repo

[data-sync-user]

We should migrate the syncstorage/tokenserver docs on https://mozilla-services.readthedocs.io/en/latest/index.html (https://github.com/mozilla-services/docs.git) to our repo.

https://mozilla-services.readthedocs.io/en/latest/storage/index.html

https://mozilla-services.readthedocs.io/en/latest/token/index.html

Most notably are the API docs:

https://mozilla-services.readthedocs.io/en/latest/storage/apis-1.5.html

https://mozilla-services.readthedocs.io/en/latest/token/apis.html

https://mozilla-services.readthedocs.io/en/latest/storage/apis-1.5.html

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