doc: add a few screenshots

README.md

@@ -3,8 +3,13 @@
 This program receives flows (currently Netflow/IPFIX), hydrates them
 with interface names (using SNMP), geo information (using MaxMind),
 and exports them to Kafka, then ClickHouse. It also exposes a web
-interface to browse the result.
+interface to browse the collected data.
+
+![Timeseries graph](docs/timeseries.png)
+
+![Sankey graph](docs/sankey.png)
 
 *Akvorado* is developed by [Free](https://www.free.fr), a French ISP,
 and is licensed under the [AGPLv3 license](LICENSE.txt). The
-[documentation](/docs/00-intro.md) is in the `docs/` directory.
+[documentation](docs/00-intro.md) is in the `docs/` directory.
+

console/data/docs/03-usage.md

@@ -89,12 +89,25 @@ instances are still running an older version).
 ## Console service
 
 `akvorado console` starts the console service. It provides a web
-console. The home page is a simple dashboard with a few metrics, some
-graphs and a recent example of flow. The console also contains this
-documentation. The most interesting page is the “visualize” tab which
+console.
+
+### Home page
+
+![Home page](home.png)
+
+The home page contains a few statistics:
+
+- number of flows received per second
+- number of exporters
+- flow repartition by AS, ports, protocols, countries, and IP families
+- last flow received
+
+### Visualize page
+
+The most interesting page is the “visualize” tab which
 allows a user to explore data using graphs.
 
-### Graph options
+![Timeseries graph](timeseries.png)
 
 The collapsible panel on the left has several options to change the
 aspect of the graph.
@@ -134,6 +147,8 @@ The URL contains the encoded parameters and can be used to share with
 others. However, currently, no stability of the options are
 guaranteed, so an URL may stop working after a few upgrades.
 
+![Sankey graph](sankey.png)
+
 ### Filter language
 
 The filter language looks like SQL with a few variations. Fields