Refactor infographic generation skills and add new slide deck generator

- Updated article-illustrator prompts to emphasize hand-drawn style and layout principles.
- Enhanced xhs-images skill with multiple style options and auto-selection based on content signals.
- Created README in Chinese for better accessibility.
- Introduced cover-image skill for generating hand-drawn style cover images with various styles.
- Developed slide-deck skill to generate professional slide outlines with detailed structure and style instructions.
- Added prompts for cover-image and slide-deck skills to guide content generation.

.claude-plugin/marketplace.json

@@ -18,7 +18,9 @@
         "./skills/gemini-web",
         "./skills/xhs-images",
         "./skills/post-to-x",
-        "./skills/article-illustrator"
+        "./skills/article-illustrator",
+        "./skills/cover-image",
+        "./skills/slide-deck"
       ]
     }
   ]