Publish a notice that PHP binaries for Windows on pecl are not official

PHP team has started producing binaries for Windows from our tarballs, and host them on their site.

Here is an example: https://pecl.php.net/package/couchbase/4.2.2/windows

The problem is that we do not know the environment where it is being compiled, do not control it, and cannot predict when they produce those binaries. They have communication channel in the mail list though.

What we should do is to make some explicit notice that if people need windows binaries, they should rather get them from the official site, because those are tested in our CI pipeline before being published.

We only control source tarball at https://pecl.php.net/package/couchbase. This is exactly the same tarball as we publish on the release notes page, but the windows binaries are different, and those are created by PHP team.