Add new `:ignore:` tag

[krollins-mdb]

Bluehawk should have an :ignore: tag that prevents Bluehawk from parsing lines within the tag. I ran into an issue with Bluehawk trying to process C++ code: CHECK(user.state() == realm::User::state::logged_in);

Bluehawk thought that :state: was meant for it.

Could potentially address that kind of thing on an SDK basis, but there are likely similar situations that are difficult to anticipate. An :ignore: tag would provide an escape hatch for edge cases.