v1.4.0

1. Replace direct call to alexnet with calls to
   imagePretrainedNetwork("alexnet") and expand on the instructions
   around how to change networks.
2. Update most remaining plots that hardcode colors to use SeriesIndex
   colors, except in the function that recreates one of the animations
3. Include Solutions files in InstructorResources
4. Change PracticeProblemSolns.mlx to PracticeProblems.mlx and have
   PracticeProblemsSoln.mlx actually be the solutions.
5. Fix a broken link in the solutions to actually refer to a relative
   solutions file
6. Update the GitHub workflows file for more complete testing and reporting
7. Update the ProjectStartupApp.m
8. Update the project to not start Simulink in the JSD and to only use
   the app and ProjectShutdown.m
9. Update the .gitattributes file with language code names
10. Update .gitignore to standard file
11. Update links to PracticeProblems.mlx in README, MainMenu, and
    README.md
12. Update Open in MATLAB Online links in README.md