Stun fix (#18)

* make easytier-core a lib
* add stun command to easytier cli
* fix stun test for musl

easytier-cli/Cargo.toml

@@ -6,6 +6,14 @@ edition = "2021"
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
 [dependencies]
+tracing = { version = "0.1", features = ["log"] }
+tracing-subscriber = { version = "0.3", features = [
+    "env-filter",
+    "local-time",
+    "time",
+] }
+tracing-appender = "0.2.3"
+
 futures = "0.3"
 tokio = { version = "1", features = ["full"] }
 anyhow = "1.0"