Document touch zoom and aircraft update improvements

changelog.d/1378-touch-zoom-aircraft-updates.md

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+- Increase touch-first globe zoom sensitivity to three times the default while
+  retaining Cesium collision and distance limits.
+- Reuse one delayed display timestamp per civil-aircraft fleet update and cache
+  extrapolation coordinate frames until their fix coordinates change. Preserve
+  contact counts, movement cadence, tracked motion and ground corrections.