更新faq文档

[runrunrun1994]

1. 添加跑出来的结果对不上；
2. 如何 resize crop rotate 图片；
3. 如何打印 ncnn::Mat 的值；
4. 如何可视化 ncnn::Mat 的值；
5. ncnnoptimize 怎么转成 fp16 模型。

[tencent-adm]

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[nihui]

谢谢