[AUR-408] Export logs to Excel (#23)

This CL implements:

- The logic to export log to Excel.
- Route the export logic in the UI.
- Demonstrate this functionality in `./examples/promptui` project.

tests/simple_pipeline.py

@@ -0,0 +1,43 @@
+import tempfile
+from typing import List
+
+from theflow import Node
+
+from kotaemon.base import BaseComponent
+from kotaemon.embeddings import AzureOpenAIEmbeddings
+from kotaemon.llms.completions.openai import AzureOpenAI
+from kotaemon.pipelines.retrieving import RetrieveDocumentFromVectorStorePipeline
+from kotaemon.vectorstores import ChromaVectorStore
+
+
+class Pipeline(BaseComponent):
+    vectorstore_path: str = str(tempfile.mkdtemp())
+    llm: Node[AzureOpenAI] = Node(
+        default=AzureOpenAI,
+        default_kwargs={
+            "openai_api_base": "https://test.openai.azure.com/",
+            "openai_api_key": "some-key",
+            "openai_api_version": "2023-03-15-preview",
+            "deployment_name": "gpt35turbo",
+            "temperature": 0,
+            "request_timeout": 60,
+        },
+    )
+
+    @Node.decorate(depends_on=["vectorstore_path"])
+    def retrieving_pipeline(self):
+        vector_store = ChromaVectorStore(self.vectorstore_path)
+        embedding = AzureOpenAIEmbeddings(
+            model="text-embedding-ada-002",
+            deployment="embedding-deployment",
+            openai_api_base="https://test.openai.azure.com/",
+            openai_api_key="some-key",
+        )
+
+        return RetrieveDocumentFromVectorStorePipeline(
+            vector_store=vector_store, embedding=embedding
+        )
+
+    def run_raw(self, text: str) -> str:
+        matched_texts: List[str] = self.retrieving_pipeline(text)
+        return self.llm("\n".join(matched_texts)).text[0]