docs(plugin-settings): fix allowed-tools syntax to use comma-separated format

Changed allowed-tools from JSON array syntax to official comma-separated
string format per Claude Code documentation.

Fixes #82

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

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

Author: sjnims

plugins/plugin-dev/skills/plugin-settings/SKILL.md

@@ -102,7 +102,7 @@ Commands can read settings files to customize behavior:
 ```markdown
 ---
 description: Process data with plugin
-allowed-tools: ["Read", "Bash"]
+allowed-tools: Read, Bash
 ---
 
 # Process Command

plugins/plugin-dev/skills/plugin-settings/examples/create-settings-command.md

@@ -1,6 +1,6 @@
 ---
 description: "Create plugin settings file with user preferences"
-allowed-tools: ["Write", "AskUserQuestion"]
+allowed-tools: Write, AskUserQuestion
 ---
 
 # Create Plugin Settings