Added matching async load func to PlaywrightURLLoader (#5938)

Fixes # (issue)

The existing PlaywrightURLLoader load() function uses a synchronous
browser which is not compatible with jupyter.
This PR adds a sister function aload() which can be run insisde a
notebook.

---------

Co-authored-by: Harrison Chase <hw.chase.17@gmail.com>

tests/integration_tests/document_loaders/test_url_playwright.py

@@ -1,4 +1,5 @@
 """Tests for the Playwright URL loader"""
+import pytest
 
 from langchain.document_loaders import PlaywrightURLLoader
 
@@ -19,3 +20,22 @@ def test_playwright_url_loader() -> None:
     )
     docs = loader.load()
     assert len(docs) > 0
+
+
+@pytest.mark.asyncio
+async def test_playwright_async_url_loader() -> None:
+    """Test Playwright async URL loader."""
+    urls = [
+        "https://www.youtube.com/watch?v=dQw4w9WgXcQ",
+        "https://goo.gl/maps/NDSHwePEyaHMFGwh8",
+        "https://techmeme.com",
+        "https://techcrunch.com",
+    ]
+    loader = PlaywrightURLLoader(
+        urls=urls,
+        remove_selectors=["header", "footer"],
+        continue_on_failure=False,
+        headless=True,
+    )
+    docs = await loader.aload()
+    assert len(docs) > 0