docs: add heading component in a dedicated components page

[devadula-nandan]

Closes #4771

Option 2
Add new Heading component page for documentation

Changelog

New

• new pages
  https://4905--carbondesignsystem.netlify.app/components/heading/usage/
  https://4905--carbondesignsystem.netlify.app/components/heading/style/
  https://4905--carbondesignsystem.netlify.app/components/heading/code/
  https://4905--carbondesignsystem.netlify.app/components/heading/accessibility/

• inline notification references in
  https://4905--carbondesignsystem.netlify.app/elements/typography/type-sets/
  https://4905--carbondesignsystem.netlify.app/elements/typography/code/

the content needs to be reviewed

[Kritvi-bhatia17]

Hi @devadula-nandan! Could you please check with @sstrubberg or someone from the Payload team whether this should now be updated directly in Payload or if we still need to make the change in Gatsby? Sharing the related thread for context.

[sstrubberg]

On the general @Kritvi-bhatia17, I tend to agree. We should start talking about a content freeze on our Gatsby sites. But since Nandan has done the work to bring this page to life, I see no reason to close the PR. It just means we'll need to follow this up by bringing it to Payload as well. @kennylam might be able to show Nandan how to import his MDX files directly into Payload as well.

[devadula-nandan]

The consensus in the team that time was.
We still don't know when the next website would be ready. I asked the exact same questions in the calls along with the design and got this answer to add it in gatsby. Since the next website release was uncertain at that time. But the pr was never got reviewed and got outdated at this point. Might as well open a cxp issue and close all these?