Added
- `invalid_chars` attribute for `NotFoundError` when applicable
- `url` attribute for all errors that have requested a URL
- `str(error)` will return the message attribute of the error.
Changed
- The `error` attribute for all errors have been renamed to `message`
- For BrawlAPI: `get_leaderboard` split up into `get_player_leaderboard`, `get_club_leaderboard`, and `get_brawler_leaderboard`
- For the official API: `get_rankings` split up into `get_player_rankings`, `get_club_rankings`, and `get_brawler_rankings`