DevTools: Mention more features in What's New UI for Chrome 78

Bug: 986998
Change-Id: Iab7bef3f45b6a6ae03fff1f048cfb8787990ed68
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1785797
Auto-Submit: Kayce Basques <kayce@google.com>
Commit-Queue: Kayce Basques <kayce@google.com>
Commit-Queue: Erik Luo <luoe@chromium.org>
Reviewed-by: Erik Luo <luoe@chromium.org>
Cr-Commit-Position: refs/heads/master@{#693414}

third_party/blink/renderer/devtools/front_end/help/ReleaseNoteText.js

@@ -16,6 +16,16 @@ Help.releaseNoteText = [
     version: 20,
     header: 'Highlights from the Chrome 78 update',
     highlights: [
+      {
+        title: 'Multi-client support in the Audits panel',
+        subtitle: 'Use the Audits panel in combination with other features, like Local Overrides or Request Blocking.',
+        link: 'https://developers.google.com/web/updates/2019/09/devtools#multiclient',
+      },
+      {
+        title: 'Payment Handler debugging',
+        subtitle: 'Record Payment Handler events for 3 days, even when DevTools is closed.',
+        link: 'https://developers.google.com/web/updates/2019/09/devtools#payments',
+      },
       {
         title: 'Lighthouse 5.2 in the Audits panel',
         subtitle: