Implement command for Ctrl + arrow key navigation

[tirthd16]

Ctrl + → (right arrow): Moves to the last non-empty cell in the current row
Ctrl + ← (left arrow): Moves to the first non-empty cell in the current row
Ctrl + ↑ (up arrow): Moves to the top-most non-empty cell in the current column
Ctrl + ↓ (down arrow): Moves to the last non-empty cell in the current column

Having vim keybindings for such navigation is especially useful for quickly navigating large spreadsheets.