fix: predict result

[holanlan]

This PR fixed the prediction result is always [None], and added output, the following is an example:

const predict = require('./index.js');
(async () => {
  const v1 = await predict('./0a3b6b38-fb11-451c-8a0d-b5503bc351e6.jpg');
  console.log('result:', v1);
})();

Fusing layers... 
Overriding model.yaml nc=80 with nc=2

result: {'boxes': [[135, 45, 166, 65], [53, 34, 94, 59], [260, 33, 423, 60], [464, 41, 627, 67]], 'classes': [11, 2, 1, 1], 'scores': [0.9221409559249878, 0.959892988204956, 0.964300811290741, 0.9785717725753784]}

[FeelyChau]

@rickycao-qy Could you check this PR, and bump a version, please?