linux/x11: Support window icons

[not-fl3]

No description provided.

[Garfield-hr]

Hi,

Thank you for developing this remarkable render engine.

I'm currently developing a simulation software based on miniquad on Linux. I noticed that window icon support for Linux/X11 was added in this PR, and I'm trying to implement an icon for my application.

However, despite the merged changes, I'm still unable to see any window icon on my Linux/X11 system. I've tested this with the triangle example, and the window still does not show icon (please see the attached screenshot).

Based on my debugging:

1. I've verified that the update_window_icon function is being called with the proper icon data (confirmed via debug prints)
2. The same code works correctly on Windows, where the custom icon is displayed properly
3. On my Linux/X11 system, no window icon appears

Could you help confirm if there are any additional X11-specific steps needed to properly implement the window icon functionality?

Thank you for your time.

[not-fl3]

Unfortunately it works just fine on my machine :(

I would recommend to open this as an issue, not a PR comment, this way it will not be lost in time.

[Garfield-hr]

I opened an issue in #501