Added support for cygwin guest

[zzambers]

This adds support for cygwin guest to vagrant-sshfs plugin (scenario where vagrant connects to cygwin's ssh server, running on windows guest). Support for cygwin guest can by added to vagrant by installing my vagrant-guest-cygwin plugin [1] (If support for cygwin guest is required).

Host setup:
Install vagrant-guest-cygwin plugin [1] to vagrant.

Windows guest setup:

1. Install cygwin with openssh
2. Setup sshd

• for creation of service + default config, following command should do (from cygwin terminal): ssh-host-config -y
• add keys for your user

3. Install WinFsp + SSHFS-Win

• install winfsp [2]: select all components
• from cygwin terminal: cd "/cygdrive/c/Program Files (x86)/WinFsp/opt/cygfuse/" && ./install.sh
• download and install sshfs-win [2]
• cp "/cygdrive/c/Program Files/SSHFS-Win/bin/sshfs.exe" /usr/bin

4. Create some sort of dummy sudo (e.g. [3])

[1] https://github.com/zzambers/vagrant-guest-cygwin
[2] https://winfsp.dev/rel/
[3] https://superuser.com/a/122429