Adding plugin metadata to validator

[nataliecarey]

#2296

The format I've chosen is:

{
  "meta": {
    "description": "text goes here",
    "urls": {
      "documentation": "https://example.com/",
      "releaseNotes": "https://example.com/",
      "versionHistory": "https://example.com/"
    }
  }
}

I'm allowing for two variables in the URLs

{{version}} - the version number of the plugin
{{kitVersion}} - the version number of the kit that's running

I'm using both of these variables in the govuk-prototype-kit project which has the meta set to:

  "meta": {
    "description": "Quickly make interactive, accessible and realistic prototypes of GOV.UK services.",
    "urls": {
      "documentation": "https://prototype-kit.service.gov.uk/?linkFromKit={{kitVersion}}%3A{{version}}",
      "versionHistory": "https://github.com/alphagov/govuk-prototype-kit/releases",
      "releaseNotes": "https://github.com/alphagov/govuk-prototype-kit/releases/tag/v{{version}}"
    }
  }

These variables allow plugin developers to point to release-specific URLs, and also to tailor documentation to the kit version.

I've added ?linkFromKit={{kitVersion}}%3A{{version}} to the kit documentation link so that we can show warnings on the website if we need to later for specific versions.

[BenSurgisonGDS]

Looks good to me

[BenSurgisonGDS]

Webstorm is reporting Redundant character escape '\}' in RegExp. The url.match can be replaced with url.match(/\{\{(\w+)}}/g)

[nataliecarey]

Fixed, would you mind re-reviewing?