fix(tools): use markdown headings on docspages

[bennypowers]

Allows downstream to use markdown-it plugins to manipulate output e.g. by adding hash links to headers

Unblocks RedHat-UX/red-hat-design-system#1051

What I did

1. in DocsPage templates, print headings as markdown instead of as HTML

Testing Instructions

1. compare DP to https://patternflyelements.org/, https://patternflyelements.org/get-started/, and https://patternflyelements.org/components/avatar/

[changeset-bot]

⚠️ No Changeset found

Latest commit: 498bad1

Merging this PR will not cause a version bump for any packages. If these changes should not result in a new version, you're good to go. If these changes should result in a version bump, you need to add a changeset.

This PR includes no changesets

When changesets are added to this PR, you'll see the packages that this PR includes changesets for and the associated semver types

Click here to learn what changesets are, and how to add one.

Click here if you're a maintainer who wants to add a changeset to this PR

[heyMP]

Deploy Preview isn't working. Looks like there is an error associated with floating-ui.

[bennypowers]

The error hasto do jspm's cdn provider cc @guybedford

[github-actions]

✅ Deploy Preview for patternfly-elements ready!

Name	Link
🔨 Latest commit	d02d534
😎 Deploy Preview	https://deploy-preview-2516--patternfly-elements.netlify.app/

---

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