Add new dependencies and implement TUN interface initialization

- Updated Cargo.toml to include `etherparse` and enable async feature for `tun-rs`.
- Added `ip_match_network` function in network module for IP matching.
- Implemented TUN interface initialization in `tun.rs`.
- Enhanced client handling in `client.rs` to support new features and improved message handling.
- Refactored router messages to use a structured `VpnPacket`.
- Updated settings for spell checking in VSCode.

.vscode/settings.json

@@ -0,0 +1,7 @@
+{
+  "cSpell.words": [
+    "etherparse",
+    "nodelay",
+    "xvpn"
+  ]
+}