Send confirmation email on successful photo submission

As per [ECOM-724](https://openedx.atlassian.net/browse/ECOM-724), this sends a confirmation email to the user when they successfully submit their verification photos.

@dianakhuang and @stephensanchez, could you review this when you're able?
Good question. Many of our email templates are translated line by line, so I followed that pattern; this seems to be especially true of greetings and sign-offs. There is a two-line fragment in this email which I marked for translation as a single block, since the two sentences are related to each other.

Is that enough detail for you, or do you want to dig into this further? This copy will likely see revisions, so I'm wondering if we should wait to invest time on translation until then.