:recycle: replace pikepdf with pypdfium2

[sebastianMindee]

Description

Notes:

• no type declarations for mypy on this lib, unfortunately :/
• Keeping this as draft since licensing isn't fully sorted out.

Related Issue

How Has This Been Tested

Types of changes

• [x] Docs change / refactoring / dependency upgrade
• [ ] Bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to change)
• [ ] Requires a change to the official Guide documentation.