docs(changelog): credit the stills aspect fix

changelog.d/1201-cctv-stills-aspect.md

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+- Draw CCTV stills at their source aspect on the monitor plane instead of
+  stretching them to the 16:9 canvas. Most DOT cameras publish 4:3 frames, so
+  every still was widened; they are now centered and pillarboxed on the dark
+  the placeholder already ends on (Danielslay86, #1201).