docs: improve godocs info used by main package to explain what the package is and how to use it

Signed-off-by: Ron Evans <ron@hybridgroup.com>

drivers.go

@@ -1,4 +1,42 @@
-// Package drivers is just a placeholder for the sub-packages.
-// It is here just to be able to install the package without errors using
-// go get -d github.com/tinygo-org/drivers
+// Package drivers provides a collection of hardware drivers for devices that
+// can be used together with TinyGo (https://tinygo.org).
+//
+// Here is an example in TinyGo that uses the BMP180 digital barometer:
+//
+// 		package main
+//
+// 		import (
+//     		"time"
+//     		"machine"
+//
+//     		"github.com/tinygo-org/drivers/bmp180"
+// 		)
+//
+// 		func main() {
+//     		machine.I2C0.Configure(machine.I2CConfig{})
+//     		sensor := bmp180.New(machine.I2C0)
+//     		sensor.Configure()
+//
+//     		connected := sensor.Connected()
+//     		if !connected {
+//         		println("BMP180 not detected")
+//         		return
+//     		}
+//     		println("BMP180 detected")
+//
+//     		for {
+//         		temp, _ := sensor.Temperature()
+//         		println("Temperature:", float32(temp)/1000, "ºC")
+//
+//         		pressure, _ := sensor.Pressure()
+//         		println("Pressure", float32(pressure)/100000, "hPa")
+//
+//         		time.Sleep(2 * time.Second)
+//     		}
+// 		}
+//
+// Each individual driver is contained within its own sub-package within this package and
+// there are no interdependencies in order to minimize the final size of compiled code that
+// uses any of these drivers.
+//
 package drivers