[Feature]: SEO improvements

### Issues

- [x] I have checked [existing issues](https://github.com/NTBBloodbath/norgolith/issues?q=is%3Aissue+is%3Aopen+label%3Aenhancement) and there no existing ones with the same request.

### Feature description

Auto-generate `sitemap.xml`, `robots.txt`, `OpenGraph`

### Help

Yes

### Implementation help

_No response_