added setup instructions for sudo-less RPi usage

Resolved the problem when using the SPI MOSI (GPIO 10) would result in unexpected behaviour when sending signals for a long periods. Turns out that Serial interface/ Serial port hardware has to be enabled otherwise the communication on SPI was being cut after few seconds.

Author: Kasperror

README.rst

@@ -110,6 +110,32 @@ need to be specified as it is computed from the supplied ``pixel_order``.
     pixel = neopixel.NeoPixel(board.D0, 1, pixel_order=neopixel.RGBW)
     pixel[0] = (30, 0, 20, 10)
 
+Setup for sudo-less usage on Raspberry Pi boards
+=============
+1. Enable both SPI and Serial port hardware (Serial interface). Do it by ``raspi-config`` tool or manually by adding
+
+   ::
+   
+      dtparam=spi=on
+      enable_uart=1
+
+   to the ``/boot/config.txt``
+
+2. Reboot the Pi to apply the changes - the hardware setup takes place during boot. 
+3. Connect LED's DIN to ``GPIO10`` (physical pin 19)
+
+When initializing the ``NeoPixel`` object **always** do it with ``board.D10`` (GPIO10)
+
+.. code-block:: python
+
+    import board
+    import neopixel
+    
+    DATA_PIN = board.D10
+    pixel = neopixel.NeoPixel(DATA_PIN, ...)
+
+Now you can execute the code using ``python`` without ``sudo``
+
 Documentation
 =============