Fix for extension recognition

[pwoszczyk]

Related to #323:

• Fix for symfony/http-foundation >= 5.0.0 & not installed symfony/mime
• Use of \Symfony\Component\Mime\MimeTypes as default guesser if possible
• Suggestion to use symfony/mime

[pwoszczyk]

I think a better way to solve the problem could be to update minimum supported PHP version to 7.1 and substitute symfony/http-foundation with symfony/mime, but I don't want to break backward compatibility.

[Webklex]

Hi @pwoszczyk ,
many thanks for your pull request. We are actually planing to switch to php v8.1 with the next major release (v5.0.0). It's getting tough to support both php7 and php8 at the same time.

Thanks again :)