added ff release notes for :heading pseudo-classes

[dletorey]

Description

• Added experimental release notes for :heading pseudo-class and :heading() functional pseudo-class
• Added note to the Firefox 142 release page

Motivation

• Working on issue #40483

Related issues and pull requests

• Content PR
• BCD PR

[github-actions]

Preview URLs

• /en-US/docs/Mozilla/Firefox/Experimental_features
• /en-US/docs/Mozilla/Firefox/Releases/142

Flaws (6)

URL: /en-US/docs/Mozilla/Firefox/Experimental_features
Title: Experimental features in Firefox
Flaw count: 3

• broken_links:
  • Can't resolve /en-US/docs/Web/CSS/:heading_function#functional_notation
• macros:
  • Can't resolve /en-US/docs/Web/CSS/:heading
  • Can't resolve /en-US/docs/Web/CSS/:heading_function

---

URL: /en-US/docs/Mozilla/Firefox/Releases/142
Title: Firefox 142 for developers
Flaw count: 3

• broken_links:
  • Can't resolve /en-US/docs/Web/CSS/:heading_function#functional_notation
• macros:
  • Can't resolve /en-US/docs/Web/CSS/:heading
  • Can't resolve /en-US/docs/Web/CSS/:heading_function

External URLs (2)

URL: /en-US/docs/Mozilla/Firefox/Experimental_features
Title: Experimental features in Firefox

• https://bugzil.la/1974386 (1 time) (Note! This may be a new URL 👀)

---

URL: /en-US/docs/Mozilla/Firefox/Releases/142
Title: Firefox 142 for developers

• https://bugzil.la/1974386 (1 time) (Note! This may be a new URL 👀)

(comment last updated: 2025-08-11 14:50:49)

[dipikabh]

Looking good, thank you!

[github-actions]

This pull request has merge conflicts that must be resolved before it can be merged.