add training materials from NE BRR 2023 docker training

[kapsakcj]

Setting as a draft for now, since I'd like to add links to the training materials on the main /README.md but wanted to at least get the ball rolling on this PR. Will mark ready for review once that is completed.

I realized we never PR'd this back to the main StaPH-B repo.

@kevinlibuit I would like to get your eyes on these training materials before merging. Happy to make edits where you see necessary.

This PR does the following:

• adds the Powerpoint slides (PDF) used in lecture
• markdown document which walks the trainee through the various exercises
• updates the .gitpod.yml folder to git checkout master instead of main which resolves the issue of checking out the repo upon launching the GitPod (see screenshot of GitPod workspace I just spun up)

Pull Request (PR) checklist:

• Include a description of what is in this pull request in this message.
• The dockerfile successfully builds to a test target for the user creating the PR. (i.e. docker build --tag samtools:1.15test --target test docker-builds/samtools/1.15 )
• Directory structure as name of the tool in lower case with special characters removed with a subdirectory of the version number (i.e. spades/3.12.0/Dockerfile)
  • (optional) All test files are located in same directory as the Dockerfile (i.e. shigatyper/2.0.1/test.sh)
• Create a simple container-specific README.md in the same directory as the Dockerfile (i.e. spades/3.12.0/README.md)
  • If this README is longer than 30 lines, there is an explanation as to why more detail was needed
• Dockerfile includes the recommended LABELS
• Main README.md has been updated to include the tool and/or version of the dockerfile(s) in this PR
• Program_Licenses.md contains the tool(s) used in this PR and has been updated for any missing