feature: faceit and premier leaderboard tabs

[lukepolo]

The web half of 5stackgg/api#411: two new leaderboard tabs, Faceit (rating, with skill level beside it) and Premier (rank).

They ride the existing leaderboard page, so paging, sorting and jump-to-your-rank come for free. Two differences from the other tabs:

• The filter bar is hidden. Scope, match type, role, source and exclude-tournaments all narrow matches played here, and these are ratings cached from FACEIT and from parsed Premier demos. A scope of "last 7 days" sitting above them would read as applied when it is not.
• Each tab only appears where the platform collects that rating: Faceit when the FACEIT import is on, Premier when external matches are on. A stock instance with neither sees neither tab.

Translations: 16/16 locales, composed from the words each locale already uses for Faceit, Premier, ELO, Level and Rank.

Tests: 98.