Create IMU as gyro example

[Krabbenhoft]

This is an explanation of how to program the IMU as a gyro sensor. https://github.com/gamemanual0/gm0/issues/416

[seakrueger]

Hello,

Currently, your page is not being built or linted by sphinx because it is missing the ".rst" file extension. Also in order for your page to be discoverable, you need to add "imu" as an entry in the software/tutorials/index.rst file

[Krabbenhoft]

Thank you. I will address these issues.

[NoahAndrews]

Using an IMU as a gyro sensor would mean getting just the rotational velocity from it. Using the computed orientation data from an IMU is really the opposite of "using it as a gyro".