Add Ctrl+Delete keyboard shortcut to delete word forward

[heidarkermanzamin]

Title: Add Ctrl+Delete keyboard shortcut to delete word forward

Description:

On most text editors (VS Code, Sublime, etc.), Ctrl+Delete deletes the word to the right of the cursor. Mark Text currently supports Ctrl+Backspace (delete word backward) but lacks the forward equivalent.

Expected behavior:

• Cursor at "hello |world" → Ctrl+Delete → "hello |"
• Cursor at "hello| world" → Ctrl+Delete → "hello| "

Current behavior:
Ctrl+Delete does nothing or triggers system behavior (depending on OS).

Environment:

• Ubuntu [version]
• Mark Text [version]

Additional context:
This is a standard editing shortcut across most text editors and would improve consistency and productivity in Mark Text.