Directory paths in README.md

Hi, I think this sentence needs a few changes.  

- .icons (which has a new PhotoGIMP icon) > .local/share/icons (which has a new PhotoGIMP icon)
- .local (which contains the personalized .desktop file) > .local/share/applications (which contains the personalized .desktop file)

https://github.com/Diolinux/PhotoGIMP/blob/master/README.md?plain=1#L42-L43
 
