Used of stdlib module removed in python 3.13

[m3at]

Hi, thanks for the useful tool,

imghdr, used in the resizer, has been removed in python3.13.
We could use one of the recommended external library, but as we only care about 3 file types (webp / jpg / png afaict) we could just check the first few bytes?

This is enough to check if it's in one of those three image types:

from typing import Optional, Union, BinaryIO

def what_img_ext(src: Union[bytes, bytearray, memoryview, BinaryIO]) -> Optional[str]:
    if isinstance(src, (bytes, bytearray, memoryview)):
        h = bytes(src[:12])
    else:
        if not (hasattr(src, "seek") and hasattr(src, "tell")):
            return None
        pos = src.tell()
        h = src.read(12)
        src.seek(pos)

    if h.startswith(b"\xFF\xD8\xFF"):
        return "jpeg"
    if h.startswith(b"\x89PNG\r\n\x1a\n"):
        return "png"
    if len(h) >= 12 and h[0:4] == b"RIFF" and h[8:12] == b"WEBP":
        return "webp"
    return None