update dep graphs

docs/graphs/README.md

@@ -0,0 +1,11 @@
+# Actix Ecosystem Dependency Graphs
+
+See rendered versions of these dot graphs [on the wiki](https://github.com/actix/actix-web/wiki/Dependency-Graph).
+
+## Rendering
+
+Dot graphs were rendered using the `dot` command from [GraphViz](https://www.graphviz.org/doc/info/command.html):
+
+```sh
+for f in $(ls docs/graphs/*.dot | xargs); do dot $f -Tpng -o${f:r}.png; done
+```