Access SSH with short-lived-cert doesn't work on Windows

Hi,

I've been following the [short-lived-cert documentation](https://developers.cloudflare.com/cloudflare-one/identity/users/short-lived-certificates), and I had no trouble setting things up on the server-side and on my Mac and Linux clients. But I haven't been able to get things working on Windows clients.

The issue appears to be with the ssh config generated by the cloudflared daemon. For example, running `cloudflared access ssh-config --hostname mysever.mydomain.com --short-lived-cert` as recommended in the docs generates the following ssh config entries:
```
Host mysever.mydomain.com
ProxyCommand bash -c 'cloudflared access ssh-gen --hostname %h; ssh -tt %r@cfpipe-mysever.mydomain.com >&2 <&1'

Host cfpipe-vm.example.com
HostName mysever.mydomain.com
ProxyCommand cloudflared access ssh --hostname %h
IdentityFile ~/.cloudflared/mysever.mydomain.com-cf_key
CertificateFile ~/.cloudflared/mysever.mydomain.com-cf_key-cert.pub
```

Copying these to the ssh config file and trying to run `ssh user@mysever.mydomain.com` returns this error on Windows (typical error when a command in ProxyCommand does not exist):
```
> ssh user@mysever.mydomain.com
CreateProcessW failed error:2
posix_spawnp: No such file or directory
```

I think I've narrowed this down to 2 issues in the generated `ProxyCommand` entry:

1. The ProxyCommand relys on bash which is not installed on Windows
2. Windows requires a full path to cloudflared.exe which is not present in the generated config.

I've tried a bit to resolve this by editing the ProxyCommand, but I haven't gotten things fully working yet. Here's what I've tried so far:

- Replacing cloudflared and ssh with full paths to the respective .exe files
- Re-writing the `ProxyCommand` to use cmd instead of bash

```
Host mysever.mydomain.com
ProxyCommand /path/to/cloudflared.exe access ssh-gen --hostname %h && /path/to/ssh.exe -tt %r@cfpipe-mysever.mydomain.com >&2 <&1

Host cfpipe-vm.example.com
HostName mysever.mydomain.com
ProxyCommand /path/to/cloudflared.exe access ssh --hostname %h
IdentityFile ~/.cloudflared/mysever.mydomain.com-cf_key
CertificateFile ~/.cloudflared/mysever.mydomain.com-cf_key-cert.pub
```

Running the ssh command with this change **does** open a browser window for Access authentication (and generates the short-lived-certs), but it **doesn't** redirect me to my remote terminal. Instead I get the following error:
```
> ssh user@myserver.mydomain.com
kex_exchange_identification: Connection closed by remote host
```

Additionally, running just the 2nd half of the ProxyCommand manually (`/path/to/ssh.exe -tt user@cfpipe-mysever.mydomain.com`) works as expected and directs me to the remote terminal.

However, the issue with this command alone is that the short-lived-certs aren't generated automatically so I won't be able to log in again after the certs expire.

Any recommendations on how to configure the SSH Config file for use on Windows?