Support to override AWS Default region

This release supports configuring AWS region through whispr configuration file:

vault: aws
secret_name: <mysecret>
env_file: .env
region: us-west-2

Note: If you set both region key and AWS_DEFAULT_REGION, region key will take precedence.

What's Changed

• feat/4: Add AWS Default region support by @narenaryan in #24

Full Changelog: v0.4.0...v0.5.0