Firefox Right-Click Prevents Further Typing

### Is this a hackmd.io issue?

- [x] Yes, the bug happens on https://hackmd.io
- [ ] No. If it's a self-hosted CodiMD instance, please fire up the issue in the repo of CodiMD: https://github.com/hackmdio/codimd

### What's the problem

#### Current behaviour
Right-clicking in the editor opens this textarea which prevents further typing in the document.
Enter, Backspace still work.
Character entry only goes into the new textarea.


#### Steps to reproduce

1. Open a document on Firefox.
2. Right-click anywhere in the document.
4. See textarea on the spot of right-click.

#### Expected behaviour

Not prevent typing.

#### Environment

Windows 11
Firefox 137.0.1 (64-bit) troubleshoot mode which disables all add-ons.

#### Additional context

Tested and doesn't occur on either Chrome or Edge.