docs(readme): add usage example for enabling text wrapping in scrollback buffer

[xeon826]

Summary

• Add documentation section "Enabling Text Wrapping" to Configuration section
• Provide clear example showing how to use after_launch callback to enable text wrapping
• Explain when the callback executes and why it's ideal for setting buffer options

Test plan

• Documentation follows existing README structure and style
• Code example is functional and follows plugin configuration patterns
• Explanation is clear and helpful for users

🤖 Generated with Claude Code

[mikesmithgh]

Thanks for the PR! I'll make some minor tweaks to make this more general and merge it