feat: Add Save Configuration with persistent storage and 500 keywords

[dinhtuandev]

Summary

This PR introduces persistent configuration storage and significantly expands the keyword dataset to improve usability and coverage.

Changes

• Implemented save/load configuration using Chrome Storage API
• Automatically load saved configuration when the popup is opened
• Added success notification UI for save actions
• Expanded keyword list to 500 diverse entries

Technical Details

• Configuration is persisted via chrome.storage.local
• State is restored on popup initialization to avoid manual reconfiguration
• Keyword expansion is isolated to a dedicated module for maintainability

Affected Files

• popup.js
• config.js
• index.html
• custom.css
• words.js

Notes

• Backward compatible with existing configurations
• No breaking changes introduced
• Happy to address feedback or adjust the implementation if needed

[dinhtuandev]

I hope you'll check it out, and if possible, merge it into your development branch and improve it further.