Features: New speeds, Instructions page, and update on background

[blakewu137]

What: This PR adds new speeds and adds an instruction page by adding a new div for the instructions and more options on the speed list.
Why: This matters because people who played the game would not know what to do and the speed was too slow.
Verified: I verified this by testing the game and the features. I expected the game to run at faster speeds with a new page. I observed that the new speeds work and the game is fully functional.

Screen.Recording.2026-01-15.095219.mp4

Status: This PR is ready for review. Next step is merging the branch with the main to make it on the file.

[NpFSHjNdg8oZCVOuyJ6XyYxkGX70xFD9]

1: The PR adds new snake speed options, an instructions page on how to play, and and updated background
2: Verification steps cannot be recreated, please add them.
3: Verification is there, but no one else can recreate them to prove verification further. To improve it, you should add steps to verify in the PR.