[FEAT] Add support for Component modelCard field

### Description
The CycloneDX Python library currently does not support the `modelCard` field on components, as defined in CycloneDX v1.5+.

### Expected behavior
- Ability to create and serialize components with type `MACHINE_LEARNING_MODEL` and the `modelCard` field populated.

### Current behavior
- The `modelCard` field is unsupported.

### Suggested solution
- Extend the Component model to include `modelCard`.
- Update JSON/XML serialization to support this field.

### References
- Parent issue: #911

Start by locating the Component model and the JSON/XML serialization entry points, then review how MACHINE_LEARNING_MODEL components are represented. Add support for the modelCard field in both serialization formats and verify that a component can create and serialize it as described; check parent issue #911 for related context.

Written by the indexing model from the issue text.