Sync studies from Lichess using Lichess OAuth API (see: #89)

[tomsihap]

Depends on: #89

Feature: Import studies from Lichess

Given the User has a Lichess account attached
When it clicks on "Fetch studies from Lichess" button
Then User has an interface to choose which studies from Lichess to import

See:

• Lichess API User's studies (looks like
  https://lichess.org/study/by/{username}/export.pgn)

It will allow users to:

• import private studies from Lichess instead of making them Unlisted if they prefer to
• easily import/sync studies from Lichess