trackball 0.2.0

Virtual Trackball Orbiting via the Exponential Map
Documentation
# Version 0.2.0 (2021-03-27)

  * Add several operation handlers.

# Version 0.1.2 (2021-03-12)

  * Fix zero literal suffixes in [C11 implementation]c11.
  * Use `num_f`, `num_d`, and `num_l` type definitions.
  * Use `None` for identity quaternion.
  * Update build script.
  * Update [README.md]README.md.

# Version 0.1.1 (2021-03-11)

  * Reliably build documentation at <https://doc.qu1x.dev/trackball>.
  * Clamp cursor/finger position between zero and maximum position.
  * Add identical [C11 implementation]c11.

# Version 0.1.0 (2021-03-06)

  * Add orbit operation handler.