fix: allow symlink folders in addPbxGroup (#16)

Author: farfromrefug

lib/pbxProject.js

@@ -588,7 +588,7 @@ pbxProject.prototype.addPbxGroup = function (filePathsArray, name, path, sourceT
         if(opt.target) {
             file.target = opt.target;
         }
-        if (fs.existsSync(filePath) && fs.lstatSync(filePath).isDirectory() && !isAssetFileType(file.lastKnownFileType)) {
+        if (fs.existsSync(filePath) && (fs.lstatSync(filePath).isDirectory() || fs.lstatSync(filePath).isSymbolicLink()) && !isAssetFileType(file.lastKnownFileType)) {
             if($path.extname(filePath) === ".lproj") {
                 continue;
             }