Added 'how-to' Videos on Homepage

The homepage initially was making a query for all Stories (that I need to optimize further, as it really shouldn't be slow), which was taking way too long and leaving a terrible impression for users. So I opted to add some quick videos in place of the query, prefetch the query for Stories, and also give a better product overview on the homepage.

Due to trying to get the MVP strengthened and maybe grab some SEO, I'm just using YouTube instead of hosting these anywhere. We'll see if this, plus some other basic UX improvements will have any impact on users coming to the site.