Add postgres and imagen skills from ai-skills collection (#19)

README.md

@@ -98,6 +98,7 @@ Claude Skills are customizable workflows that teach Claude how to perform specif
 ### Data & Analysis
 
 - [CSV Data Summarizer](https://github.com/coffeefuelbump/csv-data-summarizer-claude-skill) - Automatically analyzes CSV files and generates comprehensive insights with visualizations without requiring user prompts. *By [@coffeefuelbump](https://github.com/coffeefuelbump)*
+- [postgres](https://github.com/sanjay3290/ai-skills/tree/main/skills/postgres) - Execute safe read-only SQL queries against PostgreSQL databases with multi-connection support and defense-in-depth security. *By [@sanjay3290](https://github.com/sanjay3290)*
 - [root-cause-tracing](https://github.com/obra/superpowers/tree/main/skills/root-cause-tracing) - Use when errors occur deep in execution and you need to trace back to find the original trigger.
 
 ### Business & Marketing
@@ -120,6 +121,7 @@ Claude Skills are customizable workflows that teach Claude how to perform specif
 ### Creative & Media
 
 - [Canvas Design](./canvas-design/) - Creates beautiful visual art in PNG and PDF documents using design philosophy and aesthetic principles for posters, designs, and static pieces.
+- [imagen](https://github.com/sanjay3290/ai-skills/tree/main/skills/imagen) - Generate images using Google Gemini's image generation API for UI mockups, icons, illustrations, and visual assets. *By [@sanjay3290](https://github.com/sanjay3290)*
 - [Image Enhancer](./image-enhancer/) - Improves image and screenshot quality by enhancing resolution, sharpness, and clarity for professional presentations and documentation.
 - [Slack GIF Creator](./slack-gif-creator/) - Creates animated GIFs optimized for Slack with validators for size constraints and composable animation primitives.
 - [Theme Factory](./theme-factory/) - Applies professional font and color themes to artifacts including slides, docs, reports, and HTML landing pages with 10 pre-set themes.