Added files for Dwarf Fortress

[Plexxl]

Added files for Dwarf Fortress (used for the game downloaded from https://www.bay12games.com/dwarves/), the Arch Package, and the Steam game (https://store.steampowered.com/app/975370/Dwarf_Fortress/)

[SmartFinn]

Hmm, I notice that all icons are the same size, 64px.

[Plexxl]

After a couple days (give or take) since my last comment here, I finally updated the icons to different sized.

Hopefully this means your oldest PR can go away.

[yukina3230]

I think it's missing a steam_icon_975370 symlink

[Plexxl]

I think it's missing a steam_icon_975370 symlink

Fixed.

[yukina3230]

@SmartFinn, hopefully you’ll merge this PR — it will close #3662 and #4005

[Plexxl]

Any update?

[Plexxl]

@SmartFinn ?

[SmartFinn]

@Plexxl sorry for the late reply. I haven't had any free time to write a review.

Unfortunately, these icons aren't fixed. There are two main problems with them:

1. The scaling of all these icons isn't equal 1. It makes impossible to create a pixel-perfect icon.
   
2. And a classic issue is a lack of Pixel alignment. All edges of objects inside the icon must fit perfectly into the pixel grid.
   

Try to draw the icons from scratch instead of fixing these. It should be much easier than trying to fix an icon with wrong scaling factor.