[now-cli] Prevent framework from clearing console in `now dev` (#3903)
[now-cli] Prevent framework from clearing console in `now dev` (#3903)

When running a framework like Create React App or Gridsome, the console gets cleared. This prevented the user from seeing the message printed from `now dev` which is typically `http://localhost:3000`. Instead the user would see the framework's URL such as `http://localhost:54684`.

See #3497 for an example.

The solution is to change the child process to pipe stdout/stderr. Since most frameworks detect [`process.stdout.isTTY`](https://github.com/facebook/create-react-app/blob/7e6d6cd05f3054723c8b015c813e13761659759e/packages/react-scripts/scripts/start.js#L141-L143) before clearing the console, this will solve the problem. I was also able to intercept stdout to replace the framework's port with the `now dev` port and I think this will also help prevent confusion.

I also had to set `FORCE_COLOR=1` to avoid losing ANSI colors.

- Related to https://github.com/facebook/create-react-app/issues/2495
- Fixes #3497 
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