Add isort to the pre-commit configuration and apply it to the whole project (#595)

* Apply isort to the entire repository
* Fix missing import issues in text_to_entries
* Fix imports in migration files

tests/test_markdown_to_entries.py

@@ -1,9 +1,7 @@
-# Standard Packages
 import json
-from pathlib import Path
 import os
+from pathlib import Path
 
-# Internal Packages
 from khoj.processor.content.markdown.markdown_to_entries import MarkdownToEntries
 from khoj.utils.fs_syncer import get_markdown_files
 from khoj.utils.rawconfig import TextContentConfig