feat(parser): add entry point for cli

[saranyailla]

Issue #, if available:

Description of changes:
Initial PR with directory structure and entry point code to build the cli tool using argparse. This also includes setup script to build and install the CLI tool.

Why is this change necessary:

How was this change tested:
coverage run --source=greengrassTools -m pytest -v tests && coverage report --show-missing --fail-under=70

Any additional information or context required to review the change:

• GitHub workflow
  • Added testing and uploading coverage report to GitHub workflow.
  • Added check for minimum coverage value of 70.
  • Using python 3.6 instead of 3.9 for compatibility check with minimum version support.

Checklist:

• Updated the README if applicable
• Updated or added new unit tests
• Updated or added new integration tests
• Updated or added new end-to-end tests
• If your code makes a remote network call, it was tested with a proxy
• You confirm that the change is backwards compatible

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