DynamicImage::Bgra8 removed from upstream image crate in 0.24.x

[ajrcarey]

The upstream image crate removed enum variants relating to BGR8 from the DynamicImage enum. Upstream issue:

image-rs/image#1671

It might be possible to tell Pdfium to render using a different pixel format, or just perform some conversion ourselves. In the meantime, locked image version to ^0.23 in Cargo.toml.

[ajrcarey]

Pushed version lock as part of 0.5.3 release.

[ajrcarey]

Updated Cargo.toml to use image 0.24. Changed default setting of PdfBitmapConfig::set_reverse_byte_order() from false to true to have Pdfium render bitmaps using RGBA8 rather than the default BGRA8. Switched from using DynamicImage::Bgra8() to DynamicImage::Rgba8() in all internal code and in examples. Pushed version 0.5.4 to crates.io.

[ajrcarey]

Reversing the byte order conveniently fixes the problem of colors being reversed in WASM compared to native, which required two separate implementations of PdfColor::color(). This is now no longer necessary. Removed redundant implementation as part of release 0.5.5.