chore: update settings documentation (#756)

Automated PR to update the Settings section of the README from `flyline
--help`.

Co-authored-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>

Author: github-actions[bot]

README.md

@@ -500,6 +500,8 @@ Commands:
   suggestions           Configure suggestion behavior.
   mouse                 Configure mouse options and debugging.
   perf                  Performance profiling commands: start, stop, or dump stats.
+  changelog             Display the changelog of user-facing changes.
+  upgrade               Display instructions to upgrade flyline.
   help                  Print this message or the help of the given subcommand(s)
 
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