How many header bytes are needed form image id?

[gvasquez95]

Tried to figure it out by myself, but seems to be that docs could be misleading so I preferred to ask, given that:

1. The original Go repo says only the initial 262 bytes of a max header size are needed
2. The examples show a buffer with just 4 bytes and works for images
3. In our tests 8 bytes are good enough, obviously if 4 bytes work.

The real question is for png and jpg how many bytes are actually required to be "sliced"?

[gvasquez95]

reading on https://github.com/h2non/filetype/blob/master/matchers/image.go

seems like 4 bytes would be enough for png and jpg images.