Add new iFixit document loader (#1333)

iFixit is a wikipedia-like site that has a huge amount of open content
on how to fix things, questions/answers for common troubleshooting and
"things" related content that is more technical in nature. All content
is licensed under CC-BY-SA-NC 3.0

Adding docs from iFixit as context for user questions like "I dropped my
phone in water, what do I do?" or "My macbook pro is making a whining
noise, what's wrong with it?" can yield significantly better responses
than context free response from LLMs.

tests/integration_tests/document_loaders/__init__.py

@@ -0,0 +1 @@
+"""Test document loader integrations."""

tests/integration_tests/document_loaders/test_ifixit.py

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+from langchain.document_loaders.ifixit import IFixitLoader
+
+
+def test_ifixit_loader() -> None:
+    """Test iFixit loader."""
+    web_path = "https://www.ifixit.com/Guide/iPad+9+Battery+Replacement/151279"
+    loader = IFixitLoader(web_path)
+    assert loader.page_type == "Guide"
+    assert loader.id == "151279"
+    assert loader.web_path == web_path
+
+
+def test_ifixit_loader_teardown() -> None:
+    web_path = "https://www.ifixit.com/Teardown/Banana+Teardown/811"
+    loader = IFixitLoader(web_path)
+    """ Teardowns are just guides by a different name """
+    assert loader.page_type == "Guide"
+    assert loader.id == "811"
+
+
+def test_ifixit_loader_device() -> None:
+    web_path = "https://www.ifixit.com/Device/Standard_iPad"
+    loader = IFixitLoader(web_path)
+    """ Teardowns are just guides by a different name """
+    assert loader.page_type == "Device"
+    assert loader.id == "Standard_iPad"
+
+
+def test_ifixit_loader_answers() -> None:
+    web_path = (
+        "https://www.ifixit.com/Answers/View/318583/My+iPhone+6+is+typing+and+"
+        "opening+apps+by+itself"
+    )
+    loader = IFixitLoader(web_path)
+
+    assert loader.page_type == "Answers"
+    assert loader.id == "318583"