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/10-ourdigital-skill-creator/shared/templates/SKILL-TEMPLATE.md

@@ -0,0 +1,56 @@
+---
+name: ourdigital-{skill-name}
+description: |
+  {Brief description of the skill's purpose}
+  Activated with "ourdigital" keyword.
+
+  Triggers:
+  - "ourdigital {trigger1}", "ourdigital {trigger2}"
+  - "ourdigital-{skill-name} {action}"
+
+  Features:
+  - {Feature 1}
+  - {Feature 2}
+version: "1.0"
+author: OurDigital
+environment: {Desktop | Code | Both}
+---
+
+# OurDigital {Skill Name}
+
+{One-paragraph description of what this skill does.}
+
+## Activation
+
+Only activate when user includes "ourdigital" keyword:
+- "ourdigital {example trigger 1}"
+- "ourdigital {example trigger 2}"
+
+## Workflow
+
+### Phase 1: {Phase Name}
+
+{Description of first phase}
+
+### Phase 2: {Phase Name}
+
+{Description of second phase}
+
+### Phase 3: {Phase Name}
+
+{Description of third phase}
+
+## Output
+
+{Describe the expected outputs}
+
+## References
+
+- `shared/references/{file}.md` - {Description}
+
+## Quick Commands
+
+| Command | Action |
+|---------|--------|
+| "ourdigital {cmd1}" | {Action 1} |
+| "ourdigital {cmd2}" | {Action 2} |