Add I2C/Qwiic docs

docs/badge/qwiic.rst

+I2C / Qwiic Expansions
+====================================
+
+
+Introduction
+--------------
+
+The flow3r has two footprints for an JST-SH 4-pin connector for adding electronics.
+This connector follows the pinout for the I2C Qwiic / Stemma QT standard.
+Qwiic was developed by Sparkfun as a simple standard pinout for I2C devices.
+
+**Both Qwiic and Stemma QT are compatible with each other** and follow the same pinout and connector standard. The difference is mostly about level shifting when using 5V I2C hosts.
+Both Sparkfun and Adafruit offer a huge amount of little breakout boards that make it very easy to connect new hardware to the flow3r.
+You will also find a lot of third parties offering hardware for this standard as it has established itself as a standard I2C breakout.
+
+It is the best way to extend your flow3r with sensors and other hardware modifications.
+**The pins available can also be used for GPIO or any other bus** you desire as the ESP32-S3 has a full switch matrix and any peripheral (except Analog) can be routed to any pin.
+
+Pinout and locations
+--------------------
+The footprint on the inside is populated for you with a connector and is ready to be used.
+The footprint on the backside is not populated and you can solder a connector there if you want to use it or solder some wires to it directly.
+Keep in mind that both footprints connect to the exact same signals. It's just for convenience to offer access in multiple places.
+
+The pinout is as follows:
+::
+    1. GND
+    2. 3V3
+    3. SDA (GPIO 17)
+    4. SCL (GPIO 45)
+
+See the ESP32-S3 datasheet for more information about what else you can do with these pins. GPIO17 is also Analog capable.
+
+Here is a picture of the unpopulated backside footprint with the pinout overlayed:
+
+.. image:: assets/qwiic_pinout_overlay.jpg
+    :alt: The backside with the pinout overlayed. From left to right: SCL, SDA, 3V3, GND
+    :width: 80%
+    :align: left
+
+
+And here the excerpt from the schematic, note that there are no fixed pull ups soldered by default so you can use it with other buses without issues.
+
+.. image:: assets/qwiic_schematic.png
+   :width: 80%
+   :align: left
+
+And on the inside you can find the populated connector above the ESP32-S3.
+You can modify the 3D printed spacer with a bit of sand paper by either making the battery cable slot larger or by adding a new slot where desired.
+Or modify the source files and print your own spacer that accommodates your needs.
+
+.. image:: assets/qwiic_inside.jpg
+   :width: 80%
+   :align: left
+
+
+
+Software
+--------
+
+You can directly access the I2C bus from Micropython as ``I2C(1)``. You need firmware 1.3 or newer for this (older firmware had the wrong pins assigned).
+
+For a simple example see the I2C scanner app that comes with flow3r firmware 1.3.
+For how to use I2C in Micropython see the Micropython docs: https://docs.micropython.org/en/latest/library/machine.I2C.html
+
+I2C Scanner app: https://git.flow3r.garden/flow3r/flow3r-firmware/-/blob/main/python_payload/apps/i2c_scanner/__init__.py
+
+There is also an example of how to adapt an existing CircuitPython library to work with the flow3r with the CO2 monitor app available on the app store.
+The source code for that can be found here: https://git.flow3r.garden/timonsku/co2-monitor-scd4x
+
+Where to get hardware
+---------------------
+
+You can get cables, connectors and hardware breakout from Sparkfun, Adafruit and many other vendors.
+
+https://www.sparkfun.com/qwiic
+
+https://www.adafruit.com/category/620
+
+You can also easily buy cables and connectors from your favorite online retailer (Ebay, Amazon, Aliexpress etc) for cheap.
+
+https://www.ebay.de/sch/i.html?_nkw=jst-sh+4pin+1.0mm
+
+https://www.aliexpress.com/w/wholesale-jst-sh-4-pin-1.0mm.html
+
+https://www.amazon.de/s?k=%22jst-sh%22+4+pin+1.0mm
+
+**A good search term is "JST-SH 4-pin 1.0mm".** Many online shops will have cheap kits that have both cables and connectors for 5-8€ for a pack of 20-50.
+You also get cables that adapt to breadboard friendly jumper connectors if you want to hack something together on a breadboard.
+
+The original part number for the SMT PCB connector is **SM04B-SRSS-TB(LF)(SN)** (LCSC C160404) but you also get cheaper clones on LCSC.
+There are also vertical versions but they are not fully compatible with the footprint on the flow3r as the mechanical pads are not in the same place.
+
+.. image:: assets/qwiic-cables.jpg
+   :width: 80%
+   :align: left