Add DX Cluster Spotting page and cross-links Documents the new telnet DX Cluster feature: how it differs from the POTA/SOTA/WWFF poll-based spots, settings (host/port/login callsign, callsign-prefix and keyword filters), the table/click-to-tune behavior, and the connection rate-limit/troubleshooting details. Cross-linked from Home, POTA-and-SOTA-Spots, and the --debug-dxcluster flag added to Diagnostic-Logging.