Prompt if CLI detects that it is being invoked without a version identifier, eg. npx storybook init

[JReinhold]

When running npx storybook init (without an explicit version identifier), there are multiple outcomes and we won't know exactly what the user wants. Therefore we'll prompt users about the next action using the following logic:

if user does not specify a version on the CLI:
  if current version is latest version:
    continue with init
  elif prompt "storybook init expects a version specifier. run `npx storybook@latest init` (Y/n)":
    exec npx storybook@latest init
  else:
    echo "please run npx storybook@specifier init"