Add simple app functionality

This commit enables anyone to create a app and add 3 types of data
sources:

* pdf file
* youtube video
* website

It exposes a function called query which first gets similar docs from
vector db and then passes it to LLM to get the final answer.

embedchain/loaders/youtube_video.py

@@ -0,0 +1,22 @@
+from langchain.document_loaders import YoutubeLoader
+
+from embedchain.utils import clean_string
+
+
+class YoutubeVideoLoader:
+
+    def load_data(self, url):
+        loader = YoutubeLoader.from_youtube_url(url, add_video_info=True)
+        doc = loader.load()
+        output = []
+        if not len(doc):
+            raise ValueError("No data found")
+        content = doc[0].page_content
+        content = clean_string(content)
+        meta_data = doc[0].metadata
+        meta_data["url"] = url
+        output.append({
+            "content": content,
+            "meta_data": meta_data,
+        })
+        return output