Run the tutorial plotting code in doctests

[bhazelton]

Description

Ensure that the plotting commands in the tutorial are actually run in the doctests. Recently a bug was discovered in the plotting code because it wasn't being tested (see #1336).

Also include the generated plots in the docs for completeness.

See the RTD build to see what the docs will look like.

Motivation and Context

Fixes #1339

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation change (documentation changes only)
• Version change
• Build or continuous integration change

Checklist:

• I have read the contribution guide.
• My code follows the code style of this project.

Documentation change checklist:

• Any updated docstrings use the numpy docstring format.
• If this is a significant change to the readme or other docs, I have checked that they are rendered properly on ReadTheDocs. (you may need help to get this branch to build on RTD, just ask!)

Build or continuous integration change checklist:

• If required or optional dependencies have changed (including version numbers), I have updated the readme to reflect this.
• If this is a new CI setup, I have added the associated badge to the readme and to references/make_index.py (if appropriate).

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (e0ff8db) 99.92% compared to head (57ade93) 99.92%.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1374   +/-   ##
=======================================
  Coverage   99.92%   99.92%           
=======================================
  Files          36       36           
  Lines       20249    20249           
=======================================
  Hits        20233    20233           
  Misses         16       16           

---

Continue to review full report in Codecov by Sentry.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update e0ff8db...57ade93. Read the comment docs.

[mkolopanis]

seems pretty reasonable to me. Thanks for making sure all the images look the same too.