feat: add core func to get predictions for tz

internal/core/engine_test.go

@@ -0,0 +1,14 @@
+package core
+
+import "testing"
+
+func TestGetStatsForTZs(t *testing.T) {
+	preds, err := getStatsForTZs([]string{"+0100", "+0000"})
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if len(preds) == 0 {
+		t.Fatalf("failed to get predictions")
+	}
+}