docs(changelog): flight trails and SIGNAL LOST (#1654)

changelog.d/1654-flight-trails-signal-lost.md

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+- A tracked flight's trail splits at feed gaps, impossible jumps and reports
+  without altitude instead of joining a day of history into one line, keeps
+  every history point, and follows the path the aircraft was drawn along so it
+  no longer cuts across turns. A tracked aircraft that stops reporting shows
+  STALE, keeps flying on its last heading for five minutes, then stops dimmed
+  as SIGNAL LOST and is kept ten minutes after its last report; aircraft on or
+  near the ground hold instead (Sameh Khamis, @samehkhamis, #1654).