Demo Update d26.2d

Adds ubuntu support to the demo! Ubuntu support also planned for the full release. Mac is not.

I'm not able to personally test the steam deck version, so I'm not officially "supporting" it, but I can confirm the ubuntu build works, & that online documentation insinuates that GameMaker properly interprets steam deck input, so it is likely that you'll be able to run VI on a steam deck.

Changes relative to the previous windows build:

• title screen music

• easy mode boss variants (but normal and hard are the same as each other [& as they were before])

I keep talking about how the game is "done" but not done, & while there are some QoL and art pass things left on the table, the game is in a state where I could release it today & be happy with it. I'm not going to push the release date around any further, just going to take some time with small things until launch day.