Correct French translations for "Spoiler" and "Show" keys.

The translation for Spoiler and Show keys was incorrect :
There is no accurate one-word translation for Spoiler, the English word is used in place. The Latin word from which it comes from gave a word with different meaning ("spolier", which is linked to an old meaning of the word "spoiler", as a "looter", according to Wikipedia), which can't be used, and the proposed word "becquet" is a car spoiler.
The Show key was translated as "Montrent", instead of the infinitive form "Montrer". "Voir" can also be an acceptable input (lit. "See")

The key for mail is also an issue, in regard to the official language, as the word "courriel" should have been used, although I prefer the use of "mail" and/or "email", which is more popular in use, thus not needing correction.
Yes indeed. I had not though of it.
I should have push'd a new update in the pull request with your change.