I searched for a while, and I found a vi mode, but I don't know how to enable it in ModeDevelop(opened from Unity).
For the people who are still looking for the answer, you can enable vi mode using following menu option
Edit
→ Preferences
→ Text Editor
→ Behavior
→ Navigation (use vi modes)
Older versions may have used
Tools
→ Options
→ Text Editor
→ Behavior
→ Navigation (use vi modes)