Release v1.18.1: Enhance markdown-tools with PDF image extraction

- Add extract_pdf_images.py script using PyMuPDF
- Refactor SKILL.md for clearer workflow documentation
- Update installation to use markitdown[pdf] extra
- Update marketplace version to 1.18.1
- Update markdown-tools version to 1.1.0
- Update README/README.zh-CN with new features
- Update QUICKSTART docs with in-app install instructions

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

CLAUDE.md

@@ -32,6 +32,18 @@ Skills use a three-level loading system:
 
 ### Installation Scripts
 
+**In Claude Code (in-app):**
+```text
+/plugin marketplace add daymade/claude-code-skills
+```
+
+Then:
+1. Select **Browse and install plugins**
+2. Select **daymade/claude-code-skills**
+3. Select **skill-creator**
+4. Select **Install now**
+
+**From your terminal (CLI):**
 ```bash
 # Automated installation (macOS/Linux)
 curl -fsSL https://raw.githubusercontent.com/daymade/claude-code-skills/main/scripts/install.sh | bash
@@ -73,6 +85,8 @@ cp -r skill-name ~/.claude/skills/
 # Then restart Claude Code
 ```
 
+In Claude Code, use `/plugin ...` slash commands. In your terminal, use `claude plugin ...`.
+
 ### Git Operations
 
 This repository uses standard git workflow: