Bump version to 3.1 (#8)

Author: FilipB

Makefile

@@ -15,7 +15,7 @@
 default: image
 
 HUB ?= quay.io/sail-dev
-TAG ?= 3.0
+TAG ?= 3.1
 
 lint:
 	find . -name '*.sh' -print0 | xargs -0 -r shellcheck

README.md

@@ -12,7 +12,7 @@ Istio must-gather
 
 ### Usage
 ```sh
-oc adm must-gather --image=quay.io/sail-dev/istio-must-gather:3.0
+oc adm must-gather --image=quay.io/sail-dev/istio-must-gather:3.1
 ```
 
 The command above will create a local directory with a dump of the OpenShift Service Mesh state. Note that this command will only get data related to the Service Mesh part of the OpenShift cluster.