add instructions for linux installation

[Fleeym]

hello hi hello let's stop people asking how do i linux on the discord server every 5 minutes

[Cvolton]

why are the quick links changed

[Fleeym]

i changed geode sdk installation to point you to the correct part in the markdown, the others idk they look better with .md

[Cvolton]

i dont think the links with .md would even work on the website but i should probably wait for someone actually involved in the project to take a stance

[altalk23]

is this for steam linux only

[Fleeym]

well, yeah, that's the only way you can get the game on pc

[matcool]

closing cuz outdated