Create specific_servo_parameter

From a beginners perspective: 
I just spend an hour to test my newest servo. Filling my gabs with the documentation at http://micropython-pca9685.readthedocs.io/en/latest/index.html#. From my point of view it would be easier to have a more specific example plus the simpletest.py
This is may unesseary for advanched users, but very helpfull for bloody noobs like me.

Author: Apotessar

examples/specific_servo_parameter

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+import time
+
+from board import *
+import busio
+
+# Import the PCA9685 servo module.
+from adafruit_pca9685 import servo
+
+
+# Create the I2C bus interface.
+i2c = busio.I2C(SCL, SDA)
+
+# Create a specific PCA9685 class instance, for example digital servos. 
+    # Specs of the Servo used: 
+    #   Working Frequence: 1520us/333Hz, 900-2100us
+    #   Operating Voltage: DC 3.8V-8.4V
+    #   Speed:0.18sec/60@°3.8V 0.15sec/60°@6.0V 0.09sec/60°@8.4V
+    # The address reflects the default address, if your change your adress through soldering 
+    # (See Adafruit Tutorial on 8-Channel PWM or Servo FeatherWing - Advanche use) change it.
+servos = servo.Servos(i2c, address=0x40, freq=333, min_us=900, max_us=2100, degrees=120)
+
+# Loop forever moving servo 3 between its extremes.
+# Replace the servo number 3 with the number printed on your 8-Channel PWM or Servo​ FeatherWing
+while True:
+    servos.position(3, us=900)  # 900us period is one extreme
+    time.sleep(1)
+    servos.position(3, us=2100)  # 2100us period is opposite extreme
+    time.sleep(1)