Add new plugin "Dotplot" to known plugins

docs/plugins/known-plugins.asciidoc

@@ -30,6 +30,7 @@ This list of plugins is not guaranteed to work on your version of Kibana. Instea
 * https://github.com/mstoyano/kbn_c3js_vis[C3JS Visualizations] (mstoyano)
 * https://github.com/elo7/cohort[Cohort analysis] (elo7)
 * https://github.com/DeanF/health_metric_vis[Colored Metric Visualization] (deanf)
+* https://github.com/dlumbrer/kbn_dotplot[Dotplot] (dlumbrer)
 * https://github.com/nreese/enhanced_tilemap[Enhanced Tilemap] (nreese)
 * https://github.com/ommsolutions/kibana_ext_metrics_vis[Extended Metric] (ommsolutions)
 * https://github.com/outbrain/ob-kb-funnel[Funnel Visualization] (roybass)