docs: update readme for AWS source code change

[Taylorwutianyi]

update the readme to explain how to modify the AWS lambda source code to use the environment variable ATLAS_URI

[Copilot]

Pull request overview

Updates the documentation to describe how to modify an AWS Lambda function’s source code to read the MongoDB Atlas connection string from the ATLAS_URI environment variable.

Changes:

• Add README guidance for updating lambda_function.py to use ATLAS_URI from Lambda environment variables.
• Add a new screenshot illustrating the AWS Console “Code” changes.

Reviewed changes

Copilot reviewed 1 out of 3 changed files in this pull request and generated 2 comments.

File	Description
README.md	Adds step-by-step instructions and a screenshot reference for switching to ATLAS_URI via environment variables.
readme-images/aws_code_source_modification.png	New image used by the README to illustrate the code modifications in the AWS Console.

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[Copilot]

The instructions suggest using os.environ.get("ATLAS_URI"), but they don’t mention ensuring os is imported in lambda_function.py. Consider adding a short note to import os (if it isn’t already) to avoid a runtime NameError.

Suggested change

	Navigate to **Code** tab, modify the code source to remove (or comment out) the rows for the definitions of `username` `password` and `atlas_uri`, then assign `ATLAS_URI` to `atlas_uri` using `atlas_uri = os.environ.get("ATLAS_URI")`:
	Navigate to **Code** tab, modify the code source to remove (or comment out) the rows for the definitions of `username` `password` and `atlas_uri`. Ensure that `os` is imported at the top of `lambda_function.py` (add `import os` if it is not already there), then assign `ATLAS_URI` to `atlas_uri` using `atlas_uri = os.environ.get("ATLAS_URI")`:

[Copilot]

This sentence is a bit unclear/grammatically off: consider using “lines” (instead of “rows”), and add commas between the inline identifiers (e.g., username, password, and atlas_uri) to improve readability.

Suggested change

	Navigate to **Code** tab, modify the code source to remove (or comment out) the rows for the definitions of `username` `password` and `atlas_uri`, then assign `ATLAS_URI` to `atlas_uri` using `atlas_uri = os.environ.get("ATLAS_URI")`:
	Navigate to the **Code** tab and modify the code source to remove (or comment out) the lines defining `username`, `password`, and `atlas_uri`, then assign `ATLAS_URI` to `atlas_uri` using `atlas_uri = os.environ.get("ATLAS_URI")`: