community[minor]: Firecrawl.dev integration (#20364)

Added the [FireCrawl](https://firecrawl.dev) document loader. Firecrawl
crawls and convert any website into LLM-ready data. It crawls all
accessible subpages and give you clean markdown for each.

    - **Description:** Adds FireCrawl data loader
    - **Dependencies:** firecrawl-py
    - **Twitter handle:** @mendableai 

ccing contributors: (@ericciarla @nickscamara)

---------

Co-authored-by: Bagatur <baskaryan@gmail.com>
Co-authored-by: Bagatur <22008038+baskaryan@users.noreply.github.com>

libs/community/langchain_community/document_loaders/firecrawl.py

@@ -0,0 +1,66 @@
+from typing import Iterator, Literal, Optional
+
+from langchain_core.document_loaders import BaseLoader
+from langchain_core.documents import Document
+from langchain_core.utils import get_from_env
+
+
+class FireCrawlLoader(BaseLoader):
+    """Load web pages as Documents using FireCrawl.
+
+    Must have Python package `firecrawl` installed and a FireCrawl API key. See
+        https://www.firecrawl.dev/ for more.
+    """
+
+    def __init__(
+        self,
+        url: str,
+        *,
+        api_key: Optional[str] = None,
+        mode: Literal["crawl", "scrape"] = "crawl",
+        params: Optional[dict] = None,
+    ):
+        """Initialize with API key and url.
+
+        Args:
+            url: The url to be crawled.
+            api_key: The Firecrawl API key. If not specified will be read from env var
+                FIREWALL_API_KEY. Get an API key
+            mode: The mode to run the loader in. Default is "crawl".
+                 Options include "scrape" (single url) and
+                 "crawl" (all accessible sub pages).
+            params: The parameters to pass to the Firecrawl API.
+                Examples include crawlerOptions.
+                For more details, visit: https://github.com/mendableai/firecrawl-py
+        """
+
+        try:
+            from firecrawl import FirecrawlApp  # noqa: F401
+        except ImportError:
+            raise ImportError(
+                "`firecrawl` package not found, please run `pip install firecrawl-py`"
+            )
+        if mode not in ("crawl", "scrape"):
+            raise ValueError(
+                f"Unrecognized mode '{mode}'. Expected one of 'crawl', 'scrape'."
+            )
+        api_key = api_key or get_from_env("api_key", "FIREWALL_API_KEY")
+        self.firecrawl = FirecrawlApp(api_key=api_key)
+        self.url = url
+        self.mode = mode
+        self.params = params
+
+    def lazy_load(self) -> Iterator[Document]:
+        if self.mode == "scrape":
+            firecrawl_docs = [self.firecrawl.scrape_url(self.url, params=self.params)]
+        elif self.mode == "crawl":
+            firecrawl_docs = self.firecrawl.crawl_url(self.url, params=self.params)
+        else:
+            raise ValueError(
+                f"Unrecognized mode '{self.mode}'. Expected one of 'crawl', 'scrape'."
+            )
+        for doc in firecrawl_docs:
+            yield Document(
+                page_content=doc.get("markdown", ""),
+                metadata=doc.get("metadata", {}),
+            )