update zigimg dependency and adapt to new API
Update the zigimg dependency to a newer version that changes the
fromFilePath API to require a read buffer parameter. Add 1MB read
buffers to both the image example and the Vaxis.loadImage function
to accommodate this new requirement.
This ensures the image example compiles successfully and the library
can continue to load images from file paths using the updated zigimg
interface.
Amp-Thread-ID: https://ampcode.com/threads/T-04d58023-ce84-479f-8974-6c8fad9ce9e5
Co-authored-by: Amp <amp@ampcode.com>