add apkam verbs to protocol specification

[XavierChanth]

We are missing enroll, otp and possibly other verbs if they were introduced as part of apkam.

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1. enroll verb
2. otp verb
3. keys verb
4. notify:status
5. notify:all
6. notify:fetch
7. batch

[murali-shris]

@XavierChanth Can you point me to the repo to update the docs
I notice https://github.com/atsign-foundation/at_docs is archived

[XavierChanth]

https://github.com/atsign-foundation/docs is the repo, but the preferred way to edit them is on gitbook. However this issue is asking that the specification be updated which is part of this repo.