[Python] Release 0.20.0

Added

• apply_width_attributes and apply_height_attributes options to add dimension HTML attributes from CSS properties on supported elements (table, td, th, img). #652

Changed

• Update PyO3 to 0.28.0.

Performance

• Skip selectors that reference non-existent classes, IDs, or tags.
• Faster HTML serialization for styles containing double quotes.