Alea-preprocess

- Stack overflow protection for deeply nested or broken HTML conversion

- Adding efficient directory traversal and file type detection

- Safer handling of malformed/strange PDF files
- Improved HTML/Markdown parsing

- Adding HTML5 <time> tag support for HTML conversions
- Handling edge cases for PDF gap calibration with zero width/height fonts and empty pages

- Better whitespace preservation in <pre> and <code> tags

- Improved handling of older HTML and HTML with "custom"/invalid tags