Minor update to wait for Multiplayer

Godot is being a bit annoying with online at the moment and I have no idea when multiplayer will work properly, so in the meantime here's a minor update (the file size did get lighter but there's more content, it's just more optimised than 0.0.2)

New features :

• The dirtmouth map has a proper 3D background
• New menu and deckbuilding OST by Ovvie Cohen !!

New cards :

• Soul Master
• Gluttonous Husk
• Infected Swarm
• Watcher Knight

Balancing :

• Vengefly does not occupy its lane anymore

Fixes :

• Significantly optimised card-art
• Jank when hovering opponent's totem
• Various placement masks glitches