src/Helper/MimeType.php
public static function getMimeFor(string $extension): ?string
    {
        $extensions = static::getExtensions();
        if (isset($extensions[$extension])) {
            return $extensions[$extension];
        }

        return null;
    }
public static function getMimeFor(string $extension): ?string
    {
        $extensions = static::getExtensions();
        if (isset($extensions[$extension])) {
            return $extensions[$extension];
        }

        return null;
    }
fetch mimetype for given file-extension
@param  string $extension
@return string|null