Update documentation to state that this is not a servicenow application repository

[earlduque]

ServiceNowDevProgram has many repositories that can be imported directly into ServiceNow, this is not one of them; This repository is meant to be edited directly in GitHub or any other Git-enabled IDE like VS Code.

the root readme is overwritten automatically so changes to the readme should be done on .github/templates/rootreadmetemplate.md. Pull request changes to this file will only be approved if attached to this issue.

[RajputUsman]

@earlduque