Create spectral rule to encourage use of sensitive data flag

[milkshakeuk]

SHOULD have info sensitive data flag

Create a rule to encourage inclusion of sensitive information flag to indicate that the API has operations which may contain sensitive information such as PII or PHI etc.

Acceptance Criteria

The info block should have a property called x-contains-sensitive-data of type bool which would indicate this API has operations which contain sensitive data.

Example error message

Missing or wrong 'info.x-contains-sensitive-data', should be 'boolean'.

[IgnatG]

@andreyyudin looking at this PR

#49
can we close this issue? or do we need additional work done on it?

[andreyyudin]

I think we can close? @milkshakeuk