Explainer for PA per-participant metrics (#1272)

SHA: 6395988
Reason: push, by JensenPaul

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

index.html

@@ -6,7 +6,7 @@
   <link href="https://www.w3.org/StyleSheets/TR/2021/cg-draft" rel="stylesheet">
   <meta content="Bikeshed version ac5ea272d, updated Fri Dec 6 15:45:15 2024 -0800" name="generator">
   <link href="https://wicg.github.io/turtledove/" rel="canonical">
-  <meta content="62fdc90e763d78597d1f1ae3036db539c2f0cc17" name="revision">
+  <meta content="63959887e6e3ba3ab9c000c32ba7c39e1dea11fa" name="revision">
   <meta content="dark light" name="color-scheme">
   <link href="https://www.w3.org/StyleSheets/TR/2021/dark.css" media="(prefers-color-scheme: dark)" rel="stylesheet" type="text/css">
 <style>