Retrieve stats from Runescape Highscores

Make use of Runescape highscores api to lookup player stats and auto import them if possible.
API request: https://secure.runescape.com/m=hiscore_oldschool/index_lite.ws?player=PLAYERNAME
It returns a csv list for a valid request.

- [ ] 1. Call API
- [ ] 2. Handle failed response (Name not valid or something)
- [ ] 3. Split up csv and extract levels.

Enhances #32 and works on code implemented in #39

Start by reading the code implemented in #39 and the related work in #32, then inspect the Old School RuneScape highscores API request in this issue. Verify how a valid CSV response and an invalid player response should be handled, and use the checklist as the completion criteria for importing the player levels.

Written by the indexing model from the issue text.