Update mio dependency to 0.8

Author: marcelbuesing

Cargo.toml

@@ -10,7 +10,7 @@ repository = "https://github.com/oefd/tokio-socketcan"
 [dependencies]
 socketcan = "1.7"
 futures = "0.3"
-mio = "0.7"
+mio = { version = "0.8", features = ["os-ext"] }
 libc = "0.2"
 thiserror = "1.0"
 tokio = { version = "1", features = ["net"] }