Updates to requirements.txt

[wabhijan]

When installing required packages using pip install -r requirements.txt, gotten:

ERROR: Could not find a version that satisfies the requirement PIL==6.2.0 (from versions: none) ERROR: No matching distribution found for PIL==6.2.0

I assume this is because the library name is actually Pillow, hence performing pip install Pillow==6.2.0 might be what we are looking for.