Add table support to nimPDF with comprehensive features (#49)

- Introduced a new `table.nim` module for handling table creation and rendering.
- Implemented various table features including:
  - Auto-fitting and scaling of cell content.
  - Support for merged cells and custom styling (background color, text color, borders).
  - Automatic pagination with repeated headers for long tables.
  - Text wrapping and smart font sizing to prevent overflow.
- Added example PDF documentation showcasing table functionalities.
- Updated `nimPDF.nim` and `page.nim` to integrate the new table module.

Author: bunkford