community[minor]: add proxy support to RecursiveUrlLoader (#27364)

**Description**
This PR introduces the proxies parameter to the RecursiveUrlLoader
class, allowing the user to specify proxy servers for requests. This
update enables crawling through proxy servers, providing enhanced
flexibility for network configurations.
The key changes include:
  1.Added an optional proxies parameter to the constructor (__init__).
2.Updated the documentation to explain the proxies parameter usage with
an example.
3.Modified the _get_child_links_recursive method to pass the proxies
parameter to the requests.get function.



**Sample Usage**

```python
from bs4 import BeautifulSoup as Soup
from langchain_community.document_loaders.recursive_url_loader import RecursiveUrlLoader

proxies = {
    "http": "http://localhost:1080",
    "https": "http://localhost:1080",
}
url = "https://python.langchain.com/docs/concepts/#langchain-expression-language-lcel"
loader = RecursiveUrlLoader(
    url=url, max_depth=1, extractor=lambda x: Soup(x, "html.parser").text,proxies=proxies
)
docs = loader.load()
```

---------

Co-authored-by: root <root@thb>

libs/community/langchain_community/document_loaders/recursive_url_loader.py

@@ -268,6 +268,7 @@ class RecursiveUrlLoader(BaseLoader):
         base_url: Optional[str] = None,
         autoset_encoding: bool = True,
         encoding: Optional[str] = None,
+        proxies: Optional[dict] = None,
     ) -> None:
         """Initialize with URL to crawl and any subdirectories to exclude.
 
@@ -313,6 +314,16 @@ class RecursiveUrlLoader(BaseLoader):
                 encoding, unless the `encoding` argument has already been explicitly set.
             encoding: The encoding of the response. If manually set, the encoding will be
                 set to given value, regardless of the `autoset_encoding` argument.
+            proxies: A dictionary mapping protocol names to the proxy URLs to be used for requests.
+                This allows the crawler to route its requests through specified proxy servers.
+                If None, no proxies will be used and requests will go directly to the target URL.
+                Example usage:
+                ..code-block:: python
+
+                    proxies = {
+                        "http": "http://10.10.1.10:3128",
+                        "https": "https://10.10.1.10:1080",
+                    }
         """  # noqa: E501
 
         self.url = url
@@ -342,6 +353,7 @@ class RecursiveUrlLoader(BaseLoader):
         self.check_response_status = check_response_status
         self.continue_on_failure = continue_on_failure
         self.base_url = base_url if base_url is not None else url
+        self.proxies = proxies
 
     def _get_child_links_recursive(
         self, url: str, visited: Set[str], *, depth: int = 0
@@ -360,7 +372,9 @@ class RecursiveUrlLoader(BaseLoader):
         # Get all links that can be accessed from the current URL
         visited.add(url)
         try:
-            response = requests.get(url, timeout=self.timeout, headers=self.headers)
+            response = requests.get(
+                url, timeout=self.timeout, headers=self.headers, proxies=self.proxies
+            )
 
             if self.encoding is not None:
                 response.encoding = self.encoding