Update README to list all three init template options (#287)

## Summary
- Updated the README quick start section to list all three
`catalog-importer init` template options: **Backstage**, **JSM Assets
Integration**, and **Files**
- Previously only listed "Simple" and "Backstage", which was outdated

Fixes ONC-10013

## Test plan
- [x] Built the binary and ran `catalog-importer init` locally to
confirm the three options

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

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

Author: benfdking

README.md

@@ -45,8 +45,9 @@ catalog-importer init
 ```
 
 Choose from:
-- **Simple**: Start from scratch with inline data (perfect for learning)
 - **Backstage**: Import existing Backstage catalog-info.yaml files
+- **JSM Assets Integration**: Import objects from Jira Service Management (JSM) Assets
+- **Files**: Start from scratch with inline data (perfect for learning)
 
 ### 3. Set up your API key