Changed hitstun to not transition state if duration is 0

[odecay]

This means we can now have attacks which apply damage but do not interrupt other actions/state. Currently in use for the slingers rock throw attack.

[odecay]

bors merge

[bors[bot]]

Build succeeded:

• Check Rust formatting
• Clippy correctness checks (wasm32-unknown-unknown, web-target)
• Clippy correctness checks (x86_64-unknown-linux-gnu, target)