[JS Modularization]: documentation unclear when updating from previous version of the library

[elorzafe]

Describe the bug
A clear and concise description of what the bug is.

Customers are having issues when updating the library from older versions specially when using modularization. There is an error when the packages are duplicated on node_modules when installing aws-amplify and @aws-amplify/auth for example.

To Reproduce
Steps to reproduce the behavior:

1. Have an app with aws-amplify
2. Days later install @aws-amplify/auth specially after a new version is released
3. You will see errors like Auth not configured that is the symptom when there is package duplication inside node_modules

Expected behavior
Clarify that install aws-amplify and modularized packages like @aws-amplify/auth can create issues on the application
Screenshots
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Desktop (please complete the following information):

• OS: [e.g. iOS]
• Browser [e.g. chrome, safari]
• Version [e.g. 22]

Smartphone (please complete the following information):

• Device: [e.g. iPhone6]
• OS: [e.g. iOS8.1]
• Browser [e.g. stock browser, safari]
• Version [e.g. 22]

Additional context
Add any other context about the problem here.