Add govuk_frontend_toolkit subfolder to npm ignore
Add govuk_frontend_toolkit subfolder to npm ignore

The govuk_frontend_toolkit folder is created when copying files the govuk_frontend_toolkit repo.

When running `npm pack` locally, this file appears in the release when it shouldn't. 
Ensure this folder is added to .npmignore.
alphagov/govuk_frontend_toolkit_npm,alphagov/govuk_frontend_toolkit_npm