v1.7.0

Added:

- Set background image: span style
- Not saved indicator
- "All unsaved data will be lost" dialog
- Show file in explorer
- Print preview dialog
- Hotkeys for fullscreen: F11, Alt + Enter
- Arrow up/down for zoom in/zoom out
- Checkboard background

Changes:

- Some new icons
- Minor design improvements

Fixed:

- GitHub error
- A lot of fullscreen bugs