Add clarification on data capture and retention

[jeffpaul]

Is your enhancement related to a problem? Please describe.
ClassifAI doesn't capture or retain any data from a users site, but we don't (yet should) be clear about this in our readme.

Describe the solution you'd like
Add a section to the readme with copy akin to:

ClassifAI connects your WordPress site directly to the your account with specific service provider(s) (e.g. Microsoft Azure AI, IBM Watson), no data is gathered by 10up. The data gathered in our registration form is used simply to stay in touch with users so we can provide product updates and news. More information is available in the Privacy Policy on ClassifAIplugin.com.

Designs
n/a

Describe alternatives you've considered
n/a

Additional context
Initial concern from community here: https://wptavern.com/wpweekly-episode-357-cbd-e-commerce-xml-sitemaps-and-a-preview-of-wceu-2019