Add demo for stream visualization

[trappitsch]

This adds a demo for visualizing a gryo and accelerometer data from the tilt demo using egui and egui_plot. The example is fairly simple, but shows the basics. Limitations in streaming are likely due to the fact that live plotting is fairly heavy.

An option exists to run "simulated data", which shows some math functions instead of the ergot function. However, this example is running well with ergot, see James' demo here.

Axis are now also labeled. @jamesmunns: Are my scaling factors correct?

• Accelerometer limited to +-2g
• Gyro set to +-245 dps (although the chip's datasheet would indicate it's 250 dps?), - imu_timestamp I assumed is increasing by one every 1/6.66kHz?

lmk what you think :)

[jamesmunns]

I think this is wonderful, thank you @trappitsch! I'm going to merge and do a couple of touch-ups, I'll tag you in that PR.

[trappitsch]

sweet, thanks! one thing to keep in mind:

• time conversion
• gyro conversion

Those constants might still off. Pretty sure the accelerometer conversion one is correct.