Order a players completions on their stats viewer page by difficulty

[NevanSnider]

Currently its done by alphabetical order, and an order by difficulty would look much cleaner and be more useful

[stadust]

I think when we talked about this on discord, we agreed that we'd make this a toggle option. I guess the easy way would be to just give a UI element (dropdown with two options maybe?) somewhere on the stats viewer page and store whatever the user selects in a cookie. That way we don't have to deal with storing this information in the backend.

If we order them by difficulty, we should remove the bold and italic formatting (because it'll look silly IMO), and then just split the "demons beaten" thingy into three sections: main demons beaten, extended demons beaten and legacy demons beaten

[NevanSnider]

I actually disagree on the removal of bold and italics. It indicates a clear separation between the main list achievements, extended list, and italics. I think part of what makes the current one look so messy is that there is so many different font styles in a disorganized order, and putting them in order imo would look a lot nicer.

The demonlist+ addon on chrome already does this and it looks quite nice imo

Having an option to switch between them is fine, but I think that I would prefer difficulty be the default.

[stadust]

Done in #211 and #239