Set Pyinstaller, Pip environment to create reproducible builds of Khoj

- Dependency Version Pinning
  - First level dependency versions have been pinned.
  - Transitive dependencies have not been specified yet

- Testing
  - The Pyinstaller build has been only minimally tested for reproducibility
  - The Khoj package generated for PyPi have not been tested for reproducibility

- References
  - https://reproducible-builds.org/docs/source-date-epoch/
  - https://pyinstaller.org/en/stable/advanced-topics.html#creating-a-reproducible-build

.github/workflows/publish.yml

@@ -45,6 +45,10 @@ jobs:
           TWINE_USERNAME: __token__
           TWINE_PASSWORD: ${{ secrets.PYPI_API_KEY }}
         run: |
+          # Setup Environment for Reproducible Builds
+          export PYTHONHASHSEED=42
+          export SOURCE_DATE_EPOCH=$(git log -1 --pretty=%ct
+
           rm -rf dist
           python -m build
           twine check dist/*