feat: Replace cookie icon

[pixelbrackets]

The currently used cookie icon has some drawbacks:

• It has a white background instead of transparency, which looks odd on mouseover/hover effects in Matomo
• It is the only icon which uses a realistic photo instead of an illustration
• The source file is a lossy compression JPG, instead of the preferred SVG format

The new icon is an SVG. The image is public domain, see link in provided source file.

Before:

After:

Closes #32

[Findus23]

This is then the rescaled image: