Expose I2C Bus

[BrianPugh]

Feature request for future revisions of the board:

Have an unpopulated 4-pin header that exposes the i2c bus (plus power and ground) for external devices. Currently I'm just soldering a port to the resistors near the LED controller, but it'd be easy and free to just incorporate this into the board design.

[BrianPugh]

For anyone curious on how to do this, here is a zoom in of the header I added near the LED driver (chip next to the QR code behind the spacebar)

From top to bottom is (GND, VCC, SCL, SDA).