[SAK-FEA-1] Choosing the answers with keyboard

[anafro]

Issue information

• Sakurator last version when issue was suggested: 1.0.0.2
• Type: feature

Why this feature should be added?

To make learning process faster, it'd be better to add a keyboard support for answering. Moving mouse takes time, so I can add a button for every sound option (e.g. 1, 2, 3, 4, or W, A, S, D, or arrow buttons). It was implemented on Duolingo, so it's really convenient to use.

Difficulty for me

This is quite easy to implement. No more comment needed :)

Probable issues

If a user play too fast, too many petals will appear. So maybe I should reduce petal count that appear on the screen.