function extractedGlyphs(category, lang, weight) {
  const pathInProject = 
    `build-files/extracted/${category}-${lang.toLowerCase()}/${weight}.json`;
  const fullPath = expandPath(pathInProject);
  if (!fs.existsSync(fullPath))
    throw Error(`Extracted glyphs ${pathInProject} are not found.`);
  return readJSON(pathInProject);
}
The path to the extracted glyphs of a certain gid category and weight
@param { 'base-scale' | 'center-scale' | 'lengthen' | 'punc-like' } category 
Gid category
@param { 'J' | 'K' | 'SC' | 'TC' } lang    Language tag
@param { 'ExtraLight' | 'Light' | 'Normal' | 'Regular' | 'Medium' | 'Bold' 
| 'Heavy' } weight  Weight
@returns { { [key:string]: { advanceWidth: number, contours: GlyphData } } } 
Path of the extracted glyphs