Incorrect mime providing headerBytes

[phath9]

Steps to reproduce:

1. Get a sample PNG file: https://upload.wikimedia.org/wikipedia/sco/a/aa/Bart_Simpson_200px.png
2. Use lookupMimeType method: lookupMimeType('Bart_Simpson_200px.png', headerBytes: [0xFF, 0xD8]);
3. It returns image/jpeg when expected result should be image/png

[mx1up]

if you want to pass header bytes, they should be coming from the file itself.
in your sample code, you passed hard coded header bytes which would be matching a jpeg, so it's logical it returns image/jpeg