feat: add defaults to theme-urls.json output on build

[adamstankiewicz]

Description

Extends build-scss.js Node.js script to include optional --defaultThemeVariants option to customize the default theme variants to include in the theme-urls.json output.

node build-scss.js --defaultThemeVariants light
node build-scss.js --defaultThemeVariants light dark

Ensures the theme-urls.json output looks like the following, with the additional of the defaults object property in favor of the previous default and dark properties:

{
  "themeUrls": {
    "core": {
      "paths": {
        "default": "./core.css",
        "minified": "./core.min.css"
      }
    },
    "defaults": {
      "light": "light"
    },
    "variants": {
      "light": {
        "paths": {
          "default": "./light.css",
          "minified": "./light.min.css"
        }
      }
    }
  }
}

Deploy Preview

N/A

Merge Checklist

• If your update includes visual changes, have they been reviewed by a designer? Send them a link to the Netlify deploy preview, if applicable.
• Does your change adhere to the documented style conventions?
• Do any prop types have missing descriptions in the Props API tables in the documentation site (check deploy preview)?
• Were your changes tested using all available themes (see theme switcher in the header of the deploy preview, under the "Settings" icon)?
• Were your changes tested in the example app?
• Is there adequate test coverage for your changes?
• Consider whether this change needs to reviewed/QA'ed for accessibility (a11y). If so, please add wittjeff and adamstankiewicz as reviewers on this PR.

Post-merge Checklist

• Verify your changes were released to NPM at the expected version.
• If you'd like, share your contribution in #show-and-tell.
• 🎉 🙌 Celebrate! Thanks for your contribution.

[netlify]

✅ Deploy Preview for paragon-openedx ready!

Name	Link
🔨 Latest commit	151216e
🔍 Latest deploy log	https://app.netlify.com/sites/paragon-openedx/deploys/64bd447a2d72f50008a5e648
😎 Deploy Preview	https://deploy-preview-2468--paragon-openedx.netlify.app
📱 Preview on mobile	Toggle QR Code... Use your smartphone camera to open QR code link.

---

To edit notification comments on pull requests, go to your Netlify site configuration.

[edx-semantic-release]

🎉 This PR is included in version 21.0.0-alpha.40 🎉

The release is available on:

• npm package (@alpha dist-tag)
• GitHub release

Your semantic-release bot 📦🚀

[edx-semantic-release]

🎉 This PR is included in version 22.0.0-alpha.1 🎉

The release is available on:

• npm package (@alpha dist-tag)
• GitHub release

Your semantic-release bot 📦🚀

[openedx-semantic-release-bot]

🎉 This PR is included in version 23.0.0-alpha.1 🎉

The release is available on:

• npm package (@alpha dist-tag)
• GitHub release

Your semantic-release bot 📦🚀

[openedx-semantic-release-bot]

🎉 This PR is included in version 23.0.0 🎉

The release is available on:

• npm package (@latest dist-tag)
• GitHub release

Your semantic-release bot 📦🚀

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 91.58%. Comparing base (cc022bb) to head (151216e).
Report is 874 commits behind head on alpha.

Additional details and impacted files

@@           Coverage Diff           @@
##            alpha    #2468   +/-   ##
=======================================
  Coverage   91.58%   91.58%           
=======================================
  Files         214      214           
  Lines        3519     3519           
  Branches      852      852           
=======================================
  Hits         3223     3223           
  Misses        288      288           
  Partials        8        8           

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.