add basic filetypes

[vtolstov]

please add text , json, yaml ...

[h2non]

Only binary files can be supported with the current lookup mechanism. For text-based files context inferring is required. That is outside of the purpose of this library and won't be supported.

Also, you can check file fotmat based on file extension, but that's gives you any real guarantee.

[vtolstov]

Thanks, i'm try this detection and after that fallback to mime.TypeByExt