Add haveibeenpwned sample function

Idea from Matthew Holt, using the haveibeenpwned API to query
whether a password has been found in a data-breach.

Signed-off-by: Alex Ellis (VMware) <alexellis2@gmail.com>

sample-functions/haveibeenpwned/handler_test.go

@@ -0,0 +1,22 @@
+package function
+
+import (
+	"encoding/json"
+	"testing"
+)
+
+func Test_Handle(t *testing.T) {
+	res := Handle([]byte("test1234"))
+
+	result := result{}
+	err := json.Unmarshal([]byte(res), &result)
+	if err != nil {
+		t.Errorf("unable to unmarshal response, error: %s", err)
+		t.Fail()
+	}
+
+	if result.Found == 0 {
+		t.Errorf("expected test1234 to be found several times")
+		t.Fail()
+	}
+}