Minor tweaks to the example in the Display extension doc

[brianmarco]

A few tweaks to the example mentioned in the Display extension documentation.

• Moved the device_address argument from the Display instantiation to the SSD1306 instantiation. Display doesn't currently support this argument, but SSD1306 does (https://github.com/KMKfw/kmk_firmware/blob/master/kmk/extensions/display.py#L137)
• Added missing comma to the arguments for the Display instantiation.

[xs5871]

Looks good. One thing: the device_address value is the same as the default. I think we should clarify that, i.e. comment it out as optional and add that 0x3C is the default and only needs to be changed if necessary -- just to avoid confusion and duplicate code proliferation.

[brianmarco]

Thanks for the review @xs5871 . I applied your feedback as suggested. I also applied the same feedback to the width argument for Display, and adjusted the dim_target argument to make it different from the default.

[xs5871]

Cool, thanks.