xdg: Add .desktop entry and temp ladybird icons

[hansejo]

Add a .desktop entry so that ladybird can be launched from most Linux desktop environments. Icons are temporary and were sourced from the SerenityOS browser, upscaled where needed.

Currently not installed by build system, since this is most relevant to Linux package maintainers.

I have tested this on Arch Linux running KDE, I am hoping others can test with there setups.

[ADKaster]

I'm not sure if that's the correct location for this kind of data, but if we do accept it, could you make the icon versions of this (poorly edited) version of the icon Andreas used on his most recent blog post? https://github.com/ADKaster/ladybird/blob/android-hax/android/res/drawable/ladybird_icon.png

[hansejo]

I'm not sure if that's the correct location for this kind of data, but if we do accept it, could you make the icon versions of this (poorly edited) version of the icon Andreas used on his most recent blog post? https://github.com/ADKaster/ladybird/blob/android-hax/android/res/drawable/ladybird_icon.png

I wasn't aware you did one, I tried to add a glow effect around it to mask the white background. Let me know what you think?