Add TypeScript definitions and documentation for cv.face.createFacemarkLBF

[Copilot]

The face module (part of opencv_contrib) is not included in the default opencv.js build. Users requesting cv.face.createFacemarkLBF need either a custom build or alternative approaches.

Changes

• TypeScript definitions (src/types/opencv/face.ts): Complete type definitions for Facemark, FacemarkLBF, FacemarkLBF_Params, and face namespace
• Documentation (doc/FACE_MODULE.md): Build instructions for opencv.js + opencv_contrib, alternative approaches (FaceDetectorYN, CascadeClassifier), usage examples with memory management
• Example (doc/face-example.ts): Type-safe implementation demonstrating landmark detection workflow
• README: Added opencv_contrib module availability section

Usage

The type definitions enable IntelliSense for both custom and default builds:

// Works with custom opencv.js build (opencv + opencv_contrib)
const facemark = cv.face.createFacemarkLBF();
facemark.loadModel('lbfmodel.yaml');

const faces = new cv.RectVector();
faceCascade.detectMultiScale(gray, faces);

const landmarks = new cv.MatVector();
const success: boolean = facemark.fit(gray, faces, landmarks);
// landmarks contains 68 Point2f per face for LBF model

Users wanting facial features have two paths: build custom opencv.js per doc/FACE_MODULE.md, or use FaceDetectorYN/CascadeClassifier from the default build.

Original prompt

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This section details on the original issue you should resolve

<issue_title>Add support for createFacemarkLBF</issue_title>
<issue_description>Is there any guide on implementing cv.face.createFacemarkLBF?</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes Add support for createFacemarkLBF #107

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