[Doc] Things we can improve the documentation

[vivianjeng]

• Data sounds unclear to developers, so we can still use reputation, then say that it can be generalized to data
• Reputation can be related to
  • KYC, identity
  • your own passport
  • social
• When we talk about data, we can have examples to save string data
  • we can hash the string, and prove the knowledge of the string