feat(demo): add demo script for PDF processing

- Create demo.py script for PDF file processing
- Implement PDF reading, classification, and inference usingOpendatalab's magic_pdf library- Add pipelines for OCR and text modes
- Include result visualization and markdown export

demo/demo.py

+# Copyright (c) Opendatalab. All rights reserved.
+import os
+
+from magic_pdf.data.data_reader_writer import FileBasedDataWriter, FileBasedDataReader
+from magic_pdf.data.dataset import PymuDocDataset
+from magic_pdf.model.doc_analyze_by_custom_model import doc_analyze
+from magic_pdf.config.enums import SupportedPdfParseMethod
+
+# args
+pdf_file_name = "demo1.pdf"  # replace with the real pdf path
+name_without_suff = pdf_file_name.split(".")[0]
+
+# prepare env
+local_image_dir, local_md_dir = "output/images", "output"
+image_dir = str(os.path.basename(local_image_dir))
+
+os.makedirs(local_image_dir, exist_ok=True)
+
+image_writer, md_writer = FileBasedDataWriter(local_image_dir), FileBasedDataWriter(
+    local_md_dir
+)
+image_dir = str(os.path.basename(local_image_dir))
+
+# read bytes
+reader1 = FileBasedDataReader("")
+pdf_bytes = reader1.read(pdf_file_name)  # read the pdf content
+
+# proc
+## Create Dataset Instance
+ds = PymuDocDataset(pdf_bytes)
+
+## inference
+if ds.classify() == SupportedPdfParseMethod.OCR:
+    infer_result = ds.apply(doc_analyze, ocr=True)
+
+    ## pipeline
+    pipe_result = infer_result.pipe_ocr_mode(image_writer)
+
+else:
+    infer_result = ds.apply(doc_analyze, ocr=False)
+
+    ## pipeline
+    pipe_result = infer_result.pipe_txt_mode(image_writer)
+
+### draw model result on each page
+infer_result.draw_model(os.path.join(local_md_dir, f"{name_without_suff}_model.pdf"))
+
+### draw layout result on each page
+pipe_result.draw_layout(os.path.join(local_md_dir, f"{name_without_suff}_layout.pdf"))
+
+### draw spans result on each page
+pipe_result.draw_span(os.path.join(local_md_dir, f"{name_without_suff}_spans.pdf"))
+
+### dump markdown
+pipe_result.dump_md(md_writer, f"{name_without_suff}.md", image_dir)
+
+### dump content list
+pipe_result.dump_content_list(md_writer, f"{name_without_suff}_content_list.json", image_dir)
\ No newline at end of file