docs: Issue263 Installation doc updates (#270)
docs: Issue263 Installation doc updates (#270)

* docs: Updated the installation doc to include a section on cloning the repo, docs on authentication, and updating Terraform instructions so that it can function

* docs: Reformat sections to be more context friendly. Add more clear language and link to Google Cloud SDK installation guide

* docs: specified terraform folder
GoogleCloudPlatform/professional-services-data-validator,GoogleCloudPlatform/professional-services-data-validator