WIP: Esp8266 Get Function (#1438)

machine/esp8266: add Pin Get() support

src/machine/machine_esp8266.go

@@ -107,6 +107,15 @@ func (p Pin) Configure(config PinConfig) {
 	}
 }
 
+// Get returns the current value of a GPIO pin when the pin is configured as an
+// input.
+func (p Pin) Get() bool {
+	// See this document for details
+	// https://www.espressif.com/sites/default/files/documentation/esp8266-technical_reference_en.pdf
+
+	return esp.GPIO.GPIO_IN.Get()&(1<<p) != 0
+}
+
 // Set sets the output value of this pin to high (true) or low (false).
 func (p Pin) Set(value bool) {
 	if value {