Update to latest Piston

[phideg]

This PR implements necessary fixes to be able to work with the latest piston_window version 0.145 0.146.

Although the code compiles and is clippy clean now it still runs into a known piston_window issue.

Therefore this PR needs top be updated, as soon as the bug fix has landed :)

The change can be tested by replacing the piston_window line in Cargo.toml with
piston_window = { git = "https://github.com/phideg/piston_window.git", branch = "fix/surface-alpha-mode" }

while waiting for the piston_window bug fix above to land, following additional changes landed in this PR:

• assets are now included into the executable.
• find_folder dependency could be removed now that assets no longer need to be located at runtime.
• README.md now explains how rusty_tetris can actually be installed. Now that assets are included a simple cargo install ... is sufficient 🚀 .
• the rust edition was updated to 2024, too