copy readme script fails if packages folder name is missing

[awentzel]

Describe the bug; what happened?
On a clean branch, now with packages ignored in .gitignore if a user executes node build/documentation/copy-package-readme.js it will fail because the packages folder is missing.

What are the steps to reproduce the issue?

1. Create a new branch tracking master
2. Execute on your CLI node build/documentation/copy-package-readme.js
3. See the errors

fs.js:120
    throw err;
    ^

Error: ENOENT: no such file or directory, ...

What behavior did you expect?
If the docs/en/packages folder does not exist it should be created first by the script.

If applicable, provide screenshots:

In what environment did you see the issue?

• OS & Device: [e.g. MacOS, iOS, Windows, Linux] on [iPhone 7, PC]

Is there any additional context?