Proposed CONTRIBUTING.md file using a standardized template

[riverma]

Purpose

• New CONTRIBUTING.md file format
• Leveraging https://nasa-ammos.github.io/slim/documentation/starter-kits/#contributing-guide-template
• ⚠ NOTE: this is a DRAFT pull-request and it needs to be customized / adapted to your repo - please commit to this PR branch with your customizations before merging!
• ⚠ NOTE: make your modifications by searching for the string INSERT in the file and replacing with appropriate values for your repo
• ⚠ NOTE: read through the file thoroughly to ensure its well adapted for your repo and your scenario, feel free to modify as needed

Proposed Changes

• [ADD] CONTRIBUTING.md file with sample content

Testing

• For live example, see: https://github.com/riverma/terraformly/blob/main/CONTRIBUTING.md

[jpl-jengelke]

We want to keep this format and reference it in the SK guide.

[riverma]

Don't think you need to customize this. Template is good as is (if that works for you) @jpl-jengelke