add R and Python to the titles of the notebooks

Author: MalteKurz

doc/examples/py_double_ml_multiway_cluster.ipynb

@@ -4,7 +4,7 @@
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "# Cluster Robust Double Machine Learning\n",
+    "# Python: Cluster Robust Double Machine Learning\n",
     "\n",
     "This example demonstrates the cluster robust features of the [DoubleML](https://docs.doubleml.org/stable/index.html) package.\n",
     "The theoretical foundations are given in Chiang et al. 2021."

doc/examples/r_double_ml_multiway_cluster.ipynb

@@ -5,7 +5,7 @@
    "id": "b0f8d234",
    "metadata": {},
    "source": [
-    "# Cluster Robust Double Machine Learning\n",
+    "# R: Cluster Robust Double Machine Learning\n",
     "\n",
     "This example demonstrates the cluster robust features of the [DoubleML](https://docs.doubleml.org/stable/index.html) package.\n",
     "The theoretical foundations are given in Chiang et al. 2021."