fix png name

iaoiui · iaoiui · commit 1ecee07cf30f · 2020-08-22T17:01:48.000+09:00
diff --git a/README.md b/README.md
@@ -69,7 +69,7 @@ deployment.apps/nginx2 created
 
 The alert can be found in your MS Teams like below.
 
-![](./assets/teams_alert.PNG)
+![](./assets/teams_alert.png)
 
 # Outside Cluster
 
