Make wordpress locale configurable

[rogervanwile]

Description

Currently Wordpress is always installed in the en_US version. With this change it is now possible to determine in which locale Wordpress should be installed. This makes it easy to test non-English plugins.

To use this feature, just add a locale to your cypress.json. If no one provided, en_US is used.

{
    "wp": {
        "locale": "de_DE"
    }
}

Change Log

• Add locale as new config setting

Types of changes (if applicable):

• [ ] Bug fix (non-breaking change which fixes an issue).
• [x] New feature (non-breaking change which adds functionality).
• [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected).

Checklist (if applicable):

• [x] Meets provided linting standards.

[rogervanwile]

@liamdefty Thanks for your input. I added a config validation rule. I don't know this schema, but I hope I have implemented the right way. I also added a regex pattern.