Default to english when word doesn't exist in translation

Editor assessment

The subject states a complete fallback rule, missing translation words fall back to English, which a reader can understand and evaluate without any diff, and the lowercase 'english' is a trivial cosmetic matter. Fix is the right type; scope is absent but the behavior description makes it unimportant; and no body is needed since the policy is fully contained in the headline, which the do-not-penalize guidance explicitly covers. Hygiene is good: imperative, no trailing period, no junk, reasonable length. A small message that completely communicates its small change, which is what the good band rewards.