Examples/horizon notebook

[kjjarvis]

Added notebook for prediction horizon feature. This is a slightly edited version of @aqitya's work.

Note: this notebook may not be included in the final released version of progpy, but is a template to be adjusted to fit our new example format.

[github-actions]

Thank you for opening this PR. Each PR into dev requires a code review. For the code review, look at the following:

• Reviewer (someone other than author) should look for bugs, efficiency, readability, testing, and coverage in examples (if relevant).
• Ensure that each PR adding a new feature should include a test verifying that feature.
• All errors from static analysis must be resolved.
• Review the test coverage reports (if there is a change) - will be added as comment on PR if there is a change
• Review the software benchmarking results (if there is a change) - will be added as comment on PR
• Any added dependencies are included in requirements.txt, setup.py, and dev_guide.rst (this document)
• All warnings from static analysis must be reviewed and resolved - if deemed appropriate.

[teubert]

Let's also rename this file to 09_Prediction? Then you can create a first heading # Prediction and set Prediction Horizon to second level heading?

[teubert]

This was replaced with #94