Read the API key from an environment variable.

[andreipope]

Description

Align instructions with the command.

Type of Change

• New feature (non-breaking change which adds functionality)
• Bug fix (non-breaking change which fixes an issue)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update
• Others

Checklist

Before you submit this PR, please make sure you have completed the following:

• I have read the CONTRIBUTING.md document.
• I have ensured my PR title is descriptive and in imperative mood.
• I have added necessary documentation (if appropriate).

Further comments