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_pdf_to_entries.py

@@ -1,10 +1,7 @@
-# Standard Packages
 import json
 import os
 
-# Internal Packages
 from khoj.processor.content.pdf.pdf_to_entries import PdfToEntries
-
 from khoj.utils.fs_syncer import get_pdf_files
 from khoj.utils.rawconfig import TextContentConfig