Image component: Ability to provide a different image for the dark theme

[conanthedev]

In certain scenarios I need to provide an alternate image for the dark theme. With the application logo, we can provide a different image with the logo and logoDark properties, but for the image component, I like the simplicity of what Writerside is doing: If a second image with the _dark suffix is present, it will be used when the dark theme is in use.

So a folder with the two images: image.png image_dark.png

And an image component defined like this:

![](image.png)

The image.png would be used with the light theme and the image_dark.png would be used in the dark theme.

[conanthedev]

The current workaround is described in #571