Release of version 2.0.4

[WeisLeDocto]

The new 2.0.4 release brings various minor improvements to Crappy:

• It adds the Phidget4AStepper Actuator, for controlling a Phidget stepper motor driver (#88)
• It adds the PhidgetWheatstoneBridge InOut, for driving a Phidget load cell conditioner (#88)
• It adds an automated GitHub workflow checking that Crappy builds and installs on the supported OS and Python versions (#89)
• It adds the DownSampler Modifier, that reduces the data rate on a given Link (#90)