fix PyPDF2 3.x page copying + rename documentation

- Added explicit page copying after cloneReaderDocumentRoot() calls
- Renamed PATCH_PDFWRITER.md to PATCH_PYPDF2_PDFWRITER.md
- Prevents 327-byte empty PDFs in PyPDF2 3.x

🤖 assisted by claude

odoo-bringout-oca-ocb-account_edi/account_edi/models/ir_actions_report.py

@@ -32,6 +32,10 @@ class IrActionsReport(models.Model):
                     # Post-process and embed the additional files.
                     writer = OdooPdfFileWriter()
                     writer.cloneReaderDocumentRoot(reader)
+                    # Copy all pages from the reader to the writer (required for PyPDF2 3.x)
+                    for page_num in range(reader.getNumPages()):
+                        page = reader.getPage(page_num)
+                        writer.addPage(page)
                     for edi_document in to_embed:
                         # The attachements on the edi documents are only system readable
                         # because they don't have res_id and res_model, here we are sure that