Add dt example

[teubert]

Extend 01 Simulation to include section on timestep.

[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.

[codecov-commenter]

Codecov Report

Merging #99 (b411f9b) into dev (e7d36a3) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##              dev      #99   +/-   ##
=======================================
  Coverage   84.22%   84.22%           
=======================================
  Files          99       99           
  Lines       10179    10179           
=======================================
  Hits         8573     8573           
  Misses       1606     1606           

[kjjarvis]

Nice example explaining step size