Add the changelog fragment for the Authoring panel

changelog.d/1472-authoring-panel.md

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+- Rename the Scenes panel to Authoring and lay it out in steps (Scene, Shots,
+  Preview, Save & share) with larger, higher-contrast text, numbered shots, a
+  tooltip on every action and buttons that are disabled when they would do
+  nothing (asturksever, #1472).