Envars added to the README docs

[Adii2202]

Fixes Issue

closes #801

Changes proposed

Check List (Check all the applicable boxes)

• [ ] My code follows the code style of this project.
• [ ] My change requires changes to the documentation.
• [ ] I have updated the documentation accordingly.
• [ ] All new and existing tests passed.
• [ ] This PR does not contain plagiarized content.
• [ ] The title of my pull request is a short description of the requested changes.

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