docs: Add installation instructions and example usage to README

[Brooke-white]

Description

Adds installation process, basic usage instructions, and overview of features in README.

Motivation and Context

Provides users with a quick setup guide and overview of how to use redshift_connector

Testing

N/A

Screenshots (if appropriate)

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)

Checklist

• Local run of python3 setup.py succeeds
• My code follows the code style of this project
• [ x ] I have read the README document
• I have added tests to cover my changes
• All new and existing tests passed
• A short description of the change has been added to the CHANGELOG

License

• By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of your choice.
  I agree

[iggarish]

Thx for the Readme update.