Two unknown characters in keyboard shortcuts cheatsheet

[myartsev]

select previous frame and select next frame have an unknown character next to them in the keyboard shortcuts cheatsheet window.

Steps to reproduce the bug

1. go to piskelapp.com
2. click on keyboard shortcuts in the bottom left corner
3. select previous frame and select next frame have an unknown character next to them

Environment details

• Operating System: Debian GNU/Linux 8 (jessie)

• Kernel: Linux 4.8.0-0.bpo.2-amd64

• browser (or offline application version): Firefox 45.7.0
  (Current stable firefox version in Debian)

Sprite details

N/A

[juliandescottes]

Thanks for the detailed bug report!

(For the record the unknown keys are supposed to represesent the up and down arrows.)

The issue comes from CheatsheetController.js in the formatKey_ method.
https://github.com/juliandescottes/piskel/blob/master/src/js/controller/dialogs/CheatsheetController.js#L155-L158

Up/Down/Left/Right keys should be represented with the entities ↑, ↓, ← and →.