Cloze mode

[MatejKastak]

This mode should act as a learning mode if you want to learn from your cards directly.

The idea is that all card bodies will be clozes and words would be missing from a

Implementation steps

1. Add cli option to anki command
2. Change the type of generated card to cloze
3. Randomly generate some words (this is left for discussion how) and mark them as cloze.