Add the ability to use .env files to the api-client

TODO

• Install https://www.npmjs.com/package/dotenv
• Update the .gitignore file in the API-Client and ignore the .env file
• Create a .env.sample file in the api-client root with the following
  • API_VERSION=v1
  • API_BASE_PATH=http://localhost:3000/
• Update API-Client install guide with a section on how to copy the .env.sample to a new .env file and make the required changes.