feat: add DocSpec DOCX test suite from NLdoc

ATTRIBUTION.json

@@ -31,5 +31,16 @@
     "tags": ["vng-ibd", "vng"],
     "donated": "2026-02-17",
     "notes": "Scraped from their website"
+  },
+  {
+    "format": "docx",
+    "path": "documents/docx/docspec/*.docx",
+    "title": "DocSpec DOCX Test Suite",
+    "author": "DocSpec",
+    "license": "CC-BY-NC-SA-4.0",
+    "source": "https://github.com/docspec/documents",
+    "tags": ["docspec"],
+    "donated": "2026-02-17",
+    "notes": "Test fixtures originating from NLdoc"
   }
 ]

ATTRIBUTION.md

@@ -43,3 +43,16 @@ This file tracks all donated documents, their authors, licenses, and sources.
 - **Donated**: 2026-02-17
 - **Notes**: Scraped from their website
 
+---
+
+## DocSpec DOCX Test Suite
+
+- **Format**: `docx`
+- **Path**: `documents/docx/docspec/*.docx`
+- **Author**: DocSpec
+- **License**: CC-BY-NC-SA-4.0
+- **Source**: https://github.com/docspec/documents
+- **Tags**: `docspec`
+- **Donated**: 2026-02-17
+- **Notes**: Test fixtures originating from NLdoc
+