added heatmap to readme

Author: tolik518

README.MD

@@ -12,6 +12,8 @@ If using docker-compose, the service will run 18:00, 18:30, 19:00, 19:30, 20:00
 So you can do fun stuff with your workout data, like doing silly grafana dashboards.
 For example, you can use the [Grafana Clickhouse plugin](https://grafana.com/grafana/plugins/grafana-clickhouse-datasource/) to visualize your workout data.
 
+![heatmap](https://r0.fyi/strong?style=dark)
+
 You can make heatmaps, like the one you have on github, or you can make a dashboard that shows your progress over time, or you can make a dashboard that shows your workout history.
 
 ![heatmap](./.github/heatmap.png)