Add keyboard shortcuts to toolbar actions

[BenVlodgi]

Description

Add standard keyboard shortcuts to toolbar actions.

• New Ctrl+N
• Open Ctrl+O
• Save Ctrl+S
• Save As... Ctrl+Alt+S
• Close Ctrl+W
• Exit Alt+F4
• About... F1

Type of change

• New feature (non-breaking change which adds functionality)

How Has This Been Tested?

I checked each shortcut myself.

Checklist:

• [x] I have performed a self-review of my code
• [ ] I have made corresponding changes to the documentation
• [x] My changes generate no new warnings
• [ ] I have added tests that prove my fix is effective or that my feature works