Update main.workflow

.github/main.workflow

@@ -3,7 +3,13 @@ workflow "Update Docker Hub Description" {
   on = "push"
 }
 
+action "Filter master branch" {
+  uses = "actions/bin/filter@master"
+  args = "branch master"
+}
+
 action "Docker Hub Description" {
+  needs = ["Filter master branch"]
   uses = "./"
   secrets = ["DOCKERHUB_USERNAME", "DOCKERHUB_PASSWORD", "DOCKERHUB_REPOSITORY"]
 }