Logic behind detectMimeType is a bit odd (or could be improved)

[uuf6429]

Current behaviour of detectMimeType():

• if file content is passed, it tries to get its mime type with finfo
• if that mime type is null or 'inconclusive', it falls back to map

In other words, we're forced to read the file contents to use this.
On the other hand, detectMimeTypeFromFile returns the mime type by checking the file contents without requiring the contents to be passed.

My expectation of the function logic would have been:

• if contents are passed, guess from contents
• otherwise, guess from file (path)
• if inconclusive, use map

i.e. in other words $contents would be optional, but it would still check the file.

https://github.com/thephpleague/mime-type-detection/blob/main/src/FinfoMimeTypeDetector.php#L54

I guess updating the behaviour now could be considered as a BC break though.