Add example demonstrating usage of session inspection

[WilliamParker]

An example demonstrating session inspection would be helpful. Things to target:

• The purposes of individual keys.
• Examples of using session inspection in debugging.
• When the use of truth maintenance impacts session inspection.

This example could then be linked from the page on session inspection in the docs. Some high-level discussion there is appropriate, but particularly when considering how truth maintenance impacts session inspection the details matter. While the information is on the docstrings that isn't necessarily the most accessible location. The changes in oracle-samples/clara-rules#386 increase the need for this.