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/pdf_file.py

@@ -0,0 +1,23 @@
+from langchain.document_loaders import PyPDFLoader
+
+from embedchain.utils import clean_string
+
+
+class PdfFileLoader:
+
+    def load_data(self, url):
+        loader = PyPDFLoader(url)
+        output = []
+        pages = loader.load_and_split()
+        if not len(pages):
+            raise ValueError("No data found")
+        for page in pages:
+            content = page.page_content
+            content = clean_string(content)
+            meta_data = page.metadata
+            meta_data["url"] = url
+            output.append({
+                "content": content,
+                "meta_data": meta_data,
+            })
+        return output