Fix skill-creator usage instructions: Use natural conversation, not script paths

The previous instructions showed incorrect direct script paths like:
  skill-creator/scripts/init_skill.py <skill-name> --path <output-dir>

These paths don't work after marketplace installation because:
1. Users install via: /plugin marketplace install daymade/claude-code-skills#skill-creator
2. Skills are installed to ~/.claude/skills/, not the user's current directory
3. skill-creator is a SKILL that guides Claude Code, not a standalone CLI tool

Correct usage:
After installing skill-creator, users simply ask Claude Code in natural language:
  "Create a new skill called my-awesome-skill in ~/my-skills"
  "Validate my skill at ~/my-skills/my-awesome-skill"
  "Package my skill at ~/my-skills/my-awesome-skill"

Claude Code, with skill-creator loaded, knows how to execute the bundled scripts
and guide users through the entire skill creation process.

Fixed in:
- README.md (English)
- README.zh-CN.md (Chinese)
- scripts/install.sh (bash)
- scripts/install.ps1 (PowerShell)

scripts/install.ps1

@@ -76,10 +76,12 @@ switch ($choice) {
         $commands += "/plugin marketplace install daymade/claude-code-skills#skill-creator"
 
         $afterInstall = @"
-After installation:
-- Initialize a skill: skill-creator/scripts/init_skill.py <skill-name> --path <output-dir>
-- Validate a skill: skill-creator/scripts/quick_validate.py /path/to/skill
-- Package a skill: skill-creator/scripts/package_skill.py /path/to/skill
+After installation, ask Claude Code:
+  "Create a new skill called my-awesome-skill in ~/my-skills"
+  "Validate my skill at ~/my-skills/my-awesome-skill"
+  "Package my skill at ~/my-skills/my-awesome-skill"
+
+Claude Code will guide you through the skill creation process!
 "@
     }
     "2" {