feat(widgets): add base64 property to image widget.

[OddSuvius]

Description

Added a new :base64 property to the (image) widget. This allows users to pass Base64-encoded image data directly to Eww, completely bypassing the need to write and read temporary image files to/from disk.

Under the hood, it decodes the string natively using glib::base64_decode and pipes the raw bytes into a GTK MemoryInputStream to be consumed efficiently by gdk_pixbuf::Pixbuf::from_stream_at_scale. It also includes graceful error handling if an invalid string is passed.

Usage

You can pass a Base64-encoded image string directly into the image widget.

;; Example of a dynamically updated base64 image
(defwidget workspace_icon [icon_data]
  (image :base64 icon_data 
         :image-width 24 
         :image-height 24 
         :preserve-aspect-ratio true))

Additional Notes

My use case:
I was building a fast DWM ipc integration and needed a better way to handle app icons. Instead of the usual annoying route of doing slow .desktop file lookups or writing temporary images to the hard drive from memory I just pass the raw _NET_WM_ICON ARGB pixel data from the X11 server encoded to Base64 straight into Eww. This skips disk I/O.

Other Potential Use Cases:

• Media Players: Scripts that fetch album art directly from APIs and can push the Base64 data directly to Eww without needing to manage a /tmp/current_album.png file.
• Notification Daemons: Passing inline notification icons directly through IPC without saving them to disk first.
  etc...

Checklist

• All widgets I've added are correctly documented.
• I added my changes to CHANGELOG.md, if appropriate.
• The documentation in the docs/content/main directory has been adjusted to reflect my changes.
• I used cargo fmt to automatically format all code before committing