Highlight does not work in vim insert mode.

[shinglyu]

Step to reproduce:

• Set Joplin editor to vim mode
• Open a note and write something. The MD viewer highlight works.
• Press i to enter insert mode, start typing something.

Expected: In the MD viewer the line being edited is highlighted
Actual: The highlight disappears

If I then press ESC to exit the insert mode, the highlight still don't show up. Only if I move the cursor around with j or k then the highlight appears again.