Implement __iter__ for convenient conversion to dict

[SengerM]

Now it is possible to convert into a dict:

from time import sleep
from sensirion_i2c_driver import I2cConnection, LinuxI2cTransceiver
from sensirion_i2c_sen5x import Sen5xI2cDevice

with LinuxI2cTransceiver('/dev/i2c-1') as i2c_transceiver:
	device = Sen5xI2cDevice(I2cConnection(i2c_transceiver))
	device.device_reset()
	device.start_measurement()
	sleep(2)
	while device.read_data_ready() is False:
		sleep(0.1)
	result = device.read_measured_values()
	result = dict(result)
	print(result)

$ python main.py 
{'mc_1p0': 3.6, 'mc_2p5': 6.4, 'mc_4p0': 8.6, 'mc_10p0': 9.6, 'ambient_rh': 45.66, 'ambient_t': 30.105, 'voc_index': 0.0, 'nox_index': nan}