Add BMML (Business Model Markup Language) schema

[hiasinho]

Summary

This PR adds support for BMML (Business Model Markup Language), a YAML-based markup language for describing business models based on Alexander Osterwalder's Business Model Canvas framework.

Changes:

• Add catalog entry for BMML schema
• Add positive test file (src/test/bmml.yaml)
• Add negative test file (src/negative_test/bmml.yaml)

Schema Details:

• File patterns: *.bmml, *.bmml.yaml, *.bmml.yml
• Schema URL: https://hiasinho.github.io/bmml/bmclang-v2.schema.json
• Project: https://github.com/hiasinho/bmml
• Documentation: https://hiasinho.github.io/bmml/

About BMML:
BMML enables teams to describe business models as structured YAML files, supporting:

• Business Model Canvas (9 building blocks)
• Value Proposition Canvas (optional detail)
• Relationship tracking between entities
• Schema validation and linting

The schema is hosted on GitHub Pages from the official repository.