feat: Add OurDigital custom skills package (10 skills)

Complete implementation of OurDigital skills with dual-platform support
(Claude Desktop + Claude Code) following standardized structure.

Skills created:
- 01-ourdigital-brand-guide: Brand reference & style guidelines
- 02-ourdigital-blog: Korean blog drafts (blog.ourdigital.org)
- 03-ourdigital-journal: English essays (journal.ourdigital.org)
- 04-ourdigital-research: Research prompts & workflows
- 05-ourdigital-document: Notion-to-presentation pipeline
- 06-ourdigital-designer: Visual/image prompt generation
- 07-ourdigital-ad-manager: Ad copywriting & keyword research
- 08-ourdigital-trainer: Training materials & workshop planning
- 09-ourdigital-backoffice: Quotes, proposals, cost analysis
- 10-ourdigital-skill-creator: Meta skill for creating new skills

Features:
- YAML frontmatter with "ourdigital" or "our" prefix triggers
- Standardized directory structure (code/, desktop/, shared/, docs/)
- Shared environment setup (_ourdigital-shared/)
- Comprehensive reference documentation
- Cross-skill integration support

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

custom-skills/05-ourdigital-document/desktop/skill.yaml

@@ -0,0 +1,17 @@
+name: ourdigital-document
+description: |
+  Notion-to-presentation workflow for OurDigital.
+  Activated with "ourdigital" keyword.
+
+  Triggers:
+  - "ourdigital document", "ourdigital 문서"
+  - "ourdigital presentation", "ourdigital 프레젠테이션"
+  - "ourdigital pptx", "ourdigital 발표자료"
+
+allowed-tools:
+  - mcp__plugin_Notion_notion__*
+  - mcp__plugin_figma_figma__*
+  - Read
+  - Write
+
+license: Internal-use Only