[PyCDE] Document basic functionality in 'tutorial' format and provide example code

- [ ] Document basics: modules, generators, system, ports, etc.
- [ ] Document the Type and Value systems. Discuss the difference between Python values and PyCDE Values.
- [ ] Document operator overloads,
- [ ] Document behavioral constructs.
- [ ] Ensure that said documentation is compatible with readthedocs.io.
- [ ] Create examples which are tested (via lit/cocotb/cosim) just like the 'tests'.
- [ ] Create a pipeline to rip out the testing code from the examples and publish them in the documentation. (Or vise versa.)

Start by locating the existing PyCDE documentation, examples, and tests that use lit, cocotb, or cosim. Read how current examples are structured and how Read the Docs builds the project. Done means the listed PyCDE concepts have tutorial documentation, tested examples, and a documented or working way to publish examples without their testing code.

Written by the indexing model from the issue text.