Tweak documentation for RawImage::data

[eyeplum]

Previously the asterisks (*) in the comments of RawImage::data was incorrectly interpreted as formatting characters by docs.rs, making the documentation for this field confusing to read.

It has been fixed by adding escaping before asterisks. Also tweaked formats of other mentioned fields in the comments to make them more obvious.

[eyeplum]

Before:

has widthheightcpp elements

After:

has width*height*cpp elements

[michalfita]

Language wise, * isn't proper multiplication character, but × is...

[pedrocr]

Thanks for the fix!