function searchInGlyph(glyph, xMin, xMax, yMin, yMax) {
  const result = [];
  glyph.forEach((contour, cid) => {
    contour.forEach((pt, pid) => {
      if (pt.x >= xMin && pt.x <= xMax && pt.y >= yMin && pt.y <= yMax) 
        result.push([ cid, pid ]);
    });
  });
  return result;
}
Return point indices in the glyph
@param { GlyphData } glyph 
@param { number } xMin 
@param { number } xMax 
@param { number } yMin 
@param { number } yMax 
@returns { [ number, number ][] }