FR: Zoom functionality for .cbz file reading

Does your feature request involve difficulty for you to complete a task? Please describe.

Yes. It's currently difficult to read .cbz files (such as comics or manga) because there's no zoom functionality. On smaller screens, text and artwork often appear too small, which makes the reading experience uncomfortable or even impractical.

Describe the solution you'd like

I’d like to have a zoom feature implemented for .cbz file reading, with the following behavior:

• Zoom in/out while maintaining image quality.
• Pan across the image when zoomed.
• Support for keyboard shortcuts or mouse gestures (e.g., Ctrl + scroll).
• Feature should be cross-platform and work consistently on Windows, macOS, and Linux.

Describe alternatives you've considered

I tested reading .cbz files using the ReadEra app (https://readera.org/) on mobile, which supports zoom functionality very well. However, it's only available for mobile platforms. This shows that zooming in .cbz files is technically feasible and improves the reading experience. Still, using external tools defeats the purpose of having an integrated, cross-platform reader like Readest. Other comic readers also have this feature built-in, so it's expected in a modern desktop reading tool.

Additional context

• OS: Windows 11 (but issue affects all platforms)
• Readest version: 0.9.50
• Use case: Reading .cbz comics and manga with varying image resolutions
• This feature would enhance accessibility and user experience significantly.