Add EmbedInteractiveExample macro for font-stretch page

[tannerdolby]

Mentioned in this comment that to finish the interactive example addition that the macro needed to be inserted to font-stretch.html.

URL changed: https://developer.mozilla.org/en-US/docs/Web/CSS/font-stretch

Associated Issue and PR: Completes #573 from mdn/interactive-examples. Related PR #799

[github-actions]

Preview URLs

• https://pr4608.content.dev.mdn.mozit.cloud/en-US/docs/Web/CSS/font-stretch

Flaws

URL: /en-US/docs/Web/CSS/font-stretch
Title: font-stretch
on GitHub
Flaw count: 1

• broken_links:
  • http:// external links are not allowed (will be forced to https:// at build-time)

External URLs

URL: /en-US/docs/Web/CSS/font-stretch
Title: font-stretch
on GitHub

• https://drafts.csswg.org/css-fonts-3/ (1 time)
• https://drafts.csswg.org/css-fonts-4/ (2 times)
• https://tylerfinck.com/leaguemonovariable/ (1 time)

[tannerdolby]

I moved the "Syntax" subheading above the keyword values as shown in the sibling pages near it like font-size.

Also had a look at the preview url for font-stretch and the demo is working nicely. 🎉

[wbamberg]

👍 looks good to me. Thanks for writing this example @tannerdolby !

[tannerdolby]

Ok great. Your welcome @wbamberg !