fix: set headers so playground works again

[brian-smith-tcril]

Description

Include a description of your changes here, along with a link to any relevant Jira tickets and/or Github issues.

Deploy Preview

Include a direct link to your changes in this PR's deploy preview here (e.g., a specific component page).

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 request an a11y review for the PR in the #wg-paragon Open edX Slack channel.

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.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 93.44%. Comparing base (b2da298) to head (4450844).

Additional details and impacted files

@@               Coverage Diff                @@
##           release-22.x    #3380      +/-   ##
================================================
- Coverage         93.49%   93.44%   -0.05%     
================================================
  Files               252      251       -1     
  Lines              4655     4519     -136     
  Branches           1088     1055      -33     
================================================
- Hits               4352     4223     -129     
+ Misses              296      293       -3     
+ Partials              7        3       -4     

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