Add "Fortnox" API

**Format**: OpenAPI 3.0
**Official**: NO
**Url**: https://app.swaggerhub.com/apis/VLATKOKOTEVSKI/fortnox-api/3-oas3
**Name**: Fortnox
**Category**: financial
**Logo**: https://www.fortnox.se/fortnox-text-logo-white-svg.svg
