Allow require autoloader at bin installed under vendor

[sasezaki]

copy & pasted from
https://github.com/doctrine/orm/blob/2.9.x/bin/doctrine.php

• currently, bin/sql-formatter could not be executable when installed via composer.

$ composer require --dev doctrine/sql-formatter
$ echo 'SELECT 1 FROM dual' | ./vendor/bin/sql-formatter
PHP Warning:  require_once(/mnt/d/dev/tmp/sql-formatter/vendor/doctrine/sql-formatter/bin/../vendor/autoload.php): Failed to open stream: No such file or directory in /mnt/d/dev/tmp/sql-formatter/vendor/doctrine/sql-formatter/bin/sql-formatter on line 18

[goetas]

thanks @sasezaki