Sandbox environment instructions are missing after the repo movement

[vbabuEM]

The Sandbox repo has been moved to a new place two weeks ago. During movement, a sample .env file which was there in the old repo is missing in the new repo.

Solution:

1. Please create a sample.env file and put in the required keys
2. Modify the readme.md to instruct user to create a .env file with the contents of sample.env and modify the contents to set both the BPP Client url and the Base URL.