fix: ensure 'integration' parameter is set for langchain in FireCrawlLoader (#125)

Hello,

As maintainers of the Firecrawl project, we’re introducing a new
parameter to help identify the origin of incoming requests. This PR adds
support for that parameter, allowing us to track when someone is using
our integration via `langchain`.

---------

Co-authored-by: Mason Daugherty <[email protected]>

Author: ftonato

libs/community/langchain_community/document_loaders/firecrawl.py

@@ -270,6 +270,7 @@ def __init__(
         self.params = params or {}
 
     def lazy_load(self) -> Iterator[Document]:
+        self.params['integration'] = 'langchain'
         if self.mode == "scrape":
             firecrawl_docs = [
                 self.firecrawl.scrape_url(