feature(snippet): add survey snippet for some en users

Don't merge until we get approval on the strings.
I'm guessing "No", but does this survey URL need to go through some moz.la shortener or anything? I'd assume we'd get whatever stats we may need from surveygizmo (views vs completions, etc) but thought I'd throw it out there.

And since we're not localizing this stuff we dont need to wrap those strings in `{{#t}}` blocks. \o/