Add doc file for AHT20 (#72)

aht20/doc.go

@@ -0,0 +1,17 @@
+// Copyright 2024 The Periph Authors. All rights reserved.
+// Use of this source code is governed under the Apache License, Version 2.0
+// that can be found in the LICENSE file.
+
+// Package aht20 controls an AHT20 device over I²C.
+//
+// # More details
+//
+// The sensor is a temperature and humidity sensor with a typical accuracy of ±2% RH and ±0.3°C.
+// The aht20.Dev type implements the physic.SenseEnv interface. The physic.Env measurement results
+// contain a temperature, pressure and humidity value though the pressure is not set.
+// The only device address is 0x38.
+//
+// # Datasheet
+//
+// http://www.aosong.com/userfiles/files/media/Data%20Sheet%20AHT20.pdf
+package aht20