Updated README to be more precise. Provided context about Amplify in README.

[nithinbandaru1]

Issue #, if available: #3637

Description of changes:

Problem Statement

• Currently README starts with providing Migration Guide for Amplify V2, which can be mis-interpreted as if this Repo is Amplify itself and sounds like new version of Amplify is released which is breaking change and here it is pointing to migration guide.
• I am not sure about how many people will get confused with this and raise questions like here.
  • #3637
• I am a new developer trying to create Android app for AWS services and this will make a good case to see this problem and PR reasonable to avoid unnecessary questions from beginners.
• It also looks like this not the recommended one for new app development, though it is not deprecated now, it is unlikely that this will be added/updated with new features from AWS making it one more reason to be more precise about it in README.

Solution

• Changed it to markdown Blockquotes format to show separation from Amplify and this repo.
• Added info on what is Amplify library actually and it is recommended one.
• Added info saying that this repo will be updated with security and bug fixes.

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