[Bug] File preview window not read only

[Thaodan]

Thank you for the bug report

• [X] I am using the latest version of dirvish related packages.
• [X] I checked CUSTOMIZING|EXTENSIONS.
• [X] You may also try reproduce the issue using clean environment and minimal configurations with the command emacs -Q.

Bug description

When opening Dirvish with file preview enabled the buffer containing the preview isn't read only.

Steps to reproduce

1. Open dirvish
2. M-t
3. Preview image
4. Type inside image buffer

Expected behavior

Buffer read-only

OS

Linux

Emacs Version

29

Emacs Configurations

Vanilla

Error callstack

No response

Anything else

No response