Support theme configuration via CLI

[psmyrek]

What is the motivation for adding/enhancing this feature?

It may happen that theme configuration in local.json depends on installed VSF version (i.e. some options may be invalid for older VSF version), so CLI should be able to configure downloaded theme for VSF version, which is installed.

Related issue: vuestorefront/vue-storefront#4395

What are the acceptance criteria?

• There is possibility to output local.json depending on VSF version

Can you complete this feature request by yourself?

• YES
• NO

Additional information

[benoitemile]

Could you please reflect those changes in readme.md ? because for now, when following Readme, there's no way to do the step 4, cp local.json, it's misleading.

What needs to be done first is :
yarn generate-local-config
then you can do step 4