GitLab

## Changelog
31/07/20204
- Support table recognition. Table images will be converted into html.

### how to use the new feature:
set the attribute 'table-mode' to 'true' in magic-pdf.json

### caution:
it takes 200s to 500s to convert a single table image using cpu

Introduce a Singleton pattern to manage custom models in the magic_pdf module.
This change improves the efficiency by ensuring that a single instance of the
custom model is created and reused, thereby reducing the overhead of multiple
instantiate calls for the same model configuration.

Add new configuration options for custom model directories and device modeselection. This allows users to specify the directory where models are stored
and choose between CPU and GPU modes for model inference. The configurations
are read from a JSON file and can be easily extended to support additional
options in the future.

Introduce a new feature that allows users to choose between a "lite" and a "full"
model mode for PDF document analysis. The "lite" mode uses a faster, less
accurate model, while the "full" mode employs a higher-precision model at the
cost of speed. This selection can be made through the CLI or API, providing
flexibility for different use cases.

1.Disable scaling when loading large images.
2.Moving the logic for channel conversion in image processing.