Expand suggestion blacklist

We're not able to blacklist an exhaustive list of words. We've concentrated on
words that are generally in use and considered offensive. We will add to this
list if necessary.

We have tested the 'did you mean' feature against the pattern of site-search
terms we see. Where we identified unhelpful, inappropriate or potentially
offensive suggestions, we have made sure the search terms in question don't
generate those suggestions.

For now, we've decided not to exclude legitimate words or queries that may seem
inappropriate or offensive in certain contexts.

We compiled this blacklist from a number of sources including the BBC, the
Advertising Standards Agency and Ofcom.