inset-area: property and data type: anchor positioning #6 (mdn#34462)

* inset area property

* Draft: inset-area: anchor positioning #6

* inset-area edits

* data type

* toc

* nits

* Apply suggestions from code review

Co-authored-by: Chris Mills <chrisdavidmills@gmail.com>

* underlines in links.

* Apply suggestions from code review

Co-authored-by: Chris Mills <chrisdavidmills@gmail.com>

* Update files/en-us/web/css/inset-area/index.md

Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>

* Apply suggestions from code review

Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>

* promote all headings. span all link

* links and tweaks

* Update files/en-us/web/css/inset-area_value/index.md

Co-authored-by: Chris Mills <chrisdavidmills@gmail.com>

* final final final.psd

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Co-authored-by: Chris Mills <chrisdavidmills@gmail.com>
Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>