DS3231 Alarm features (#805)

* Added alarm features
* more functions
* chore: fix typo
* feat(ds3231): add Alarm2Mode type and mode consts
* docs(ds3231): add docstrings for SQW functions
* feat(ds3231): add methods for Alarm2
* fix(ds3231): use Alarm2Mode for SetAlarm2 method
* docs(ds3231): add example for alarms
* docs(ds3231): refactor alarms example
* make main function more concise to avoid llvm error for pico
* ci(ds3231): split basic and alarm tests
* style(ds3231): reorder private funcs to the bottom
* docs(ds3231): add docstring for alarm modes
* docs(ds3231): make alarm docstrings more descriptive
* chore(ds3231): fix typo in docstring
* style(ds3231): reorder public functions
* style(ds3231): reorder private methods
* chore(ds3231): add missing error handling
* feat(ds3231): use setter funcs for en/disabling instead of separate funcs
* fix(ds3231): correctly enable alarms in example
* style(ds3231): rename SetEnable32K to SetEnabled32K for consistency
* refactor(ds3231): replace legacy with regmap package
* refactor(ds3231): use Write32 instead of Tx for SetAlarm1
* chore(ds3231): remove fmt deps and and use println in examples
* refactor(ds3231): read temperature as uint16

---------

Co-authored-by: Matthias Fulz <mfulz@olznet.de>

examples/ds3231/basic/main.go

@@ -0,0 +1,44 @@
+// Connects to an DS3231 I2C Real Time Clock (RTC).
+package main
+
+import (
+	"machine"
+	"strconv"
+	"time"
+
+	"tinygo.org/x/drivers/ds3231"
+)
+
+func main() {
+	machine.I2C0.Configure(machine.I2CConfig{})
+
+	rtc := ds3231.New(machine.I2C0)
+	rtc.Configure()
+
+	valid := rtc.IsTimeValid()
+	if !valid {
+		date := time.Date(2019, 12, 05, 20, 34, 12, 0, time.UTC)
+		rtc.SetTime(date)
+	}
+
+	running := rtc.IsRunning()
+	if !running {
+		err := rtc.SetRunning(true)
+		if err != nil {
+			println("Error configuring RTC")
+		}
+	}
+
+	for {
+		dt, err := rtc.ReadTime()
+		if err != nil {
+			println("Error reading date:", err)
+		} else {
+			println(dt.Format(time.DateTime))
+		}
+		temp, _ := rtc.ReadTemperature()
+		println("Temperature:", strconv.FormatFloat(float64(temp)/1000, 'f', -1, 32), "°C")
+
+		time.Sleep(time.Second * 1)
+	}
+}