Droplets: Add Windows Powershell example

[danaelhe]

addresses #1527 and thank you to @igpit for providing Windows powershell example. Help docs go from this:

x@x pydo % doctl compute droplet create --help
Creates a new Droplet on your account. The command requires values for the `--size`, and `--image` flags.

To retrieve a list of size slugs, use the `doctl compute size list` command. To retrieve a list of image slugs, use the `doctl compute image list` command.

If you do not specify a region, the Droplet is created in the default region for your account. If you do not specify any SSH keys, we email a temporary password to your account's email address.

Usage:
  doctl compute droplet create <droplet-name>... [flags]

Aliases:
  create, c

Examples:
The following example creates a Droplet named `example-droplet` with a two vCPUs, two GiB of RAM, and 20 GBs of disk space. The Droplet is created in the `nyc1` region and is based on the `ubuntu-20-04-x64` image. Additionally, the command uses the `--user-data` flag to run a Bash script the first time the Droplet boots up: doctl compute droplet create example-droplet --size s-2vcpu-2gb --image ubuntu-20-04-x64 --region nyc1 --user-data $'#!/bin/bash\n touch /root/example.txt; sudo apt update;sudo snap install doctl'

To this:

x@x doctl % go run cmd/doctl/main.go compute droplet create --help
Creates a new Droplet on your account. The command requires values for the `--size`, and `--image` flags.

To retrieve a list of size slugs, use the `doctl compute size list` command. To retrieve a list of image slugs, use the `doctl compute image list` command.

If you do not specify a region, the Droplet is created in the default region for your account. If you do not specify any SSH keys, we email a temporary password to your account's email address.

Usage:
  doctl compute droplet create <droplet-name>... [flags]

Aliases:
  create, c

Examples:
The following example creates a Droplet named `example-droplet` with a two vCPUs, two GiB of RAM, and 20 GBs of disk space. The Droplet is created in the `nyc1` region and is based on the `ubuntu-20-04-x64` image. Additionally, the command uses the `--user-data` flag to run a Bash script the first time the Droplet boots up:

doctl compute droplet create example-droplet --size s-2vcpu-2gb --image ubuntu-20-04-x64 --region nyc1 --user-data $'#!/bin/bash\n touch /root/example.txt; sudo apt update;sudo snap install doctl'

Please note: In Windows Powershell, the example command would be the following instead: 

doctl compute droplet create example-droplet --size s-2vcpu-2gb --image ubuntu-20-04-x64 --region nyc1  --user-data "#!/bin/bash`n touch /root/example.txt; sudo apt update;sudo snap install doctl"