Vwp/docs improved document loaders (#4006)

Huge thanks to @leo-gan for improving the document loaders notebooks

---------

Co-authored-by: Leonid Ganeline <leo.gan.57@gmail.com>

docs/modules/indexes/document_loaders/examples/duckdb.ipynb

@@ -4,15 +4,30 @@
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "# DuckDB Loader\n",
+    "# DuckDB\n",
     "\n",
-    "Load a DuckDB query with one document per row."
+    ">[DuckDB](https://duckdb.org/) is an in-process SQL OLAP database management system.\n",
+    "\n",
+    "Load a `DuckDB` query with one document per row."
    ]
   },
   {
    "cell_type": "code",
-   "execution_count": 1,
-   "metadata": {},
+   "execution_count": null,
+   "metadata": {
+    "tags": []
+   },
+   "outputs": [],
+   "source": [
+    "#!pip install duckdb"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 2,
+   "metadata": {
+    "tags": []
+   },
    "outputs": [],
    "source": [
     "from langchain.document_loaders import DuckDBLoader"
@@ -20,8 +35,10 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 2,
-   "metadata": {},
+   "execution_count": 3,
+   "metadata": {
+    "tags": []
+   },
    "outputs": [
     {
      "name": "stdout",
@@ -40,8 +57,10 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 3,
-   "metadata": {},
+   "execution_count": 4,
+   "metadata": {
+    "tags": []
+   },
    "outputs": [],
    "source": [
     "loader = DuckDBLoader(\"SELECT * FROM read_csv_auto('example.csv')\")\n",
@@ -51,8 +70,10 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 4,
-   "metadata": {},
+   "execution_count": 5,
+   "metadata": {
+    "tags": []
+   },
    "outputs": [
     {
      "name": "stdout",
@@ -167,9 +188,9 @@
    "name": "python",
    "nbconvert_exporter": "python",
    "pygments_lexer": "ipython3",
-   "version": "3.9.1"
+   "version": "3.10.6"
   }
  },
  "nbformat": 4,
- "nbformat_minor": 1
+ "nbformat_minor": 4
 }