separate section to run a fuzzer in CONTRIBUTING.md

.cargo/config.toml

@@ -1,3 +1,3 @@
 [alias]
-watch-check = ["watch", "-x", "check --examples --all-features --all --benches"]
+watch-check = ["watch", "-x", "check --examples --all-features --workspace --benches"]
 watch-test = ["watch", "-x", "test --all-features -- --skip=src/lib.rs", "-w", "src"]