Footstep replacements. Metal, carpet and glass files were left unchanged.

Grass walk, concrete walk, wood run: Kenney Impact Sounds, CC0.
https://kenney.nl/assets/impact-sounds

Grass run, concrete run, wood walk, gravel, mud, brick:
Footsteps mastered by congusbongus for C-Dogs SDL, CC BY 3.0.
https://opengameart.org/content/footsteps-on-different-surfaces
Derived from:
- swuing, footstep-grass / footstep-wood / footstep-concrete, CC BY 3.0
  https://freesound.org/people/swuing/
- Ali_6868, Gravel Footsteps, CC0
  https://freesound.org/people/Ali_6868/packs/21608/
- EminYILDIRIM, Water Footsteps, CC BY 4.0
  https://freesound.org/people/EminYILDIRIM/sounds/608663/
- ceberation, Squeaky footstep, CC BY 3.0
  https://freesound.org/people/ceberation/sounds/235524/

Snow: Corsica_S, extracted by qubodup, CC0.
https://opengameart.org/content/42-snow-and-gravel-footsteps

Ice: qubodup dry snow steps, CC0.
https://opengameart.org/content/4-dry-snow-steps

Dirt and stone: TinyWorlds, CC0.
https://opengameart.org/content/different-steps-on-wood-stone-leaves-gravel-and-mud
Dirt uses the leaf recordings at several pitches. Stone uses one recording at several pitches.
