Add support for rowspan and colspan attributes

[cscazorla]

Is your feature request related to a problem? Please describe.
The library currently does not support rendering HTML <table> elements with rowspan and colspan attributes. This limitation makes it challenging to render complex tables in PDFs where cells need to span multiple rows or columns. For example, when trying to convert the following HTML content into a PDF, the rowspan and colspan attributes are ignored, and the table layout appears incorrect:

<table>
  <tr>
    <th colspan="2">Header spanning 2 columns</th>
    <th>Header</th>
  </tr>
  <tr>
    <td rowspan="2">Row spanning 2 rows</td>
    <td>Cell</td>
    <td>Cell</td>
  </tr>
  <tr>
    <td>Cell</td>
    <td>Cell</td>
  </tr>
</table>

This limitation requires a lot of manual work to preprocess the table structure and calculate row/column spans, which is time-consuming and error-prone.

Describe the solution you'd like
I would like the library to natively support rowspan and colspan attributes when rendering HTML <table> elements. The library should automatically handle these attributes to create tables with the correct layout in the generated PDF, without requiring manual adjustments. For example, the table above should render correctly in the PDF with merged cells where appropriate.

Describe alternatives you've considered
Manual Workarounds: Preprocess the HTML content and transform it into a Flexbox-based layout to simulate the rowspan and colspan effects. This approach is complex, especially for dynamic tables with varying structures.
Switch to Other Libraries: Use libraries like wkhtmltopdf that support full HTML rendering, including rowspan and colspan. However, this would require significant changes to the application and would not leverage react-pdf/renderer.
Custom Components: Build custom React components to interpret rowspan and colspan, but this involves significant development effort and does not align with the declarative nature of react-pdf/renderer.

Additional context
We would be more than happy to donate for this feature to be implemented :)

[IV-R]

The issue at hand involves the lack of support for rowspan and colspan attributes in the react-pdf library, which complicates rendering complex tables in PDFs. To address this, consider the following detailed steps:

1. Understanding the Limitation:

react-pdf currently does not natively support rowspan and colspan attributes, leading to incorrect table layouts when these attributes are used. This necessitates manual preprocessing of table structures to achieve the desired layout.

2. Potential Solutions:

a. Manual Table Structuring:
• Flattening Cells: Manually adjust your data to represent the visual structure intended by rowspan and colspan. This involves duplicating cell content across rows or columns to simulate the spanning effect.
Example:
Instead of using:

Header spanning 2 columns
Row spanning 2 rows	Cell
	Cell

Manually create a structure without rowspan and colspan by adjusting the data to fit into individual cells appropriately.

b. Custom Table Component:
• Developing a Custom Component: Create a custom table component that interprets rowspan and colspan attributes and renders the table accordingly. This involves parsing the table data and dynamically generating the appropriate layout within react-pdf.
Considerations:
• Complexity: Implementing this requires a deep understanding of both react-pdf’s rendering process and the intricacies of table layouts.
• Maintenance: Custom solutions may require ongoing maintenance to remain compatible with future updates of react-pdf.

3. Community Engagement:
   • Feature Request: Engage with the react-pdf community by opening a feature request on the project’s GitHub repository, detailing the need for rowspan and colspan support. Provide examples and use cases to illustrate the importance of this feature.
   • Collaborative Development: If you have the necessary expertise, consider contributing to the development of this feature by submitting a pull request. Collaborate with the maintainers to ensure the implementation aligns with the project’s standards and roadmap.

4. Alternative Libraries:
   • Exploring Other Options: If immediate support for rowspan and colspan is critical, explore alternative PDF generation libraries that offer this functionality. Evaluate these libraries based on their feature set, compatibility with your project, and community support.

5. Staying Updated:
   • Monitoring Updates: Regularly check the react-pdf repository for updates or discussions related to table rendering enhancements. Participate in discussions to stay informed and contribute to the evolution of the library.