Serialport Support

- allow communication to elm327 device via a serialport
- allow creation of elm327 device without requiring unwrap()
- added some extra documentation
- expose reset() functionality of device
- serial_comm and ftdi_comm abstractions added

Cargo.toml

@@ -8,6 +8,11 @@ edition = "2021"
 
 [dependencies]
 env_logger = "0.10"
-ftdi = "0.1.3"
 log = "0.4.8"
 thiserror = "1.0.15"
+ftdi = { version = "0.1.3", optional = true }
+serialport= { version = "=4.6.1", optional = true }
+
+[features]
+ftdi_comm = [ "dep:ftdi" ]
+serialport_comm = [ "dep:serialport" ]