Wordpress installation detection doesn't work on Windows

[Vincent-HD]

Hi,
When you are on windows running the command seems to ignore wordpress installations.

The output of the command is completly empty even with many working wordpress installations in the folder:

php wp-cli.phar find "C:\laragon\www" --max_depth=4
+--------------+---------+-------+-------+
| version_path | version | depth | alias |
+--------------+---------+-------+-------+
+--------------+---------+-------+-------+

I checked a little bit in the code and it seems that the code does not support the directory separator difference between Linux and Windows.
I just added the constant DIRECTORY_SEPARATOR in the condition DIRECTORY_SEPARATOR . 'wp-includes/' === substr( $path, -13 ) when trying to detect if it's a Wordpress installations

Now the output seems to be working as expected:

php wp-cli.phar find "C:\laragon\www" --max_depth=4
+--------------------------------------------------------+---------+-------+-------+
| version_path                                           | version | depth | alias |
+--------------------------------------------------------+---------+-------+-------+
| C:\laragon\www\xxxxx\wp-includes/version.php             | 5.9      | 1     |       |
| C:\laragon\www\xxxxx\wp-includes/version.php             | 5.9      | 1     |       |
| C:\laragon\www\xxxxx\wp-includes/version.php             | 5.8.2   | 1     |       |
| C:\laragon\www\xxxxx\wp-includes/version.php             | 5.8.1   | 1     |       |
| C:\laragon\www\xxxxx\wp-includes/version.php             | 5.9      | 1     |       |
+--------------------------------------------------------+---------+-------+-------+

I didn't check the code more in-depth so I don't know if there would be side effect, I will eventually make a pull request