Add support for IPv6 addresses

## Why do you need this?
My node only has a reachable IPv6 address, so I tried to use `k3sup` with the following command:
```
k3sup install --context --user --ip
```

## Expected Behaviour
I expect this to work the same way as for an IPv4 address

## Current Behaviour

I get the following output:
```log
Running: k3sup install
2022/12/24 xx:xx:xx
Public IP:
Error: unable to connect to over ssh: dial tcp: address :22: too many colons in address
```

## Possible Solution

Add a `-6` flag for when the user wants to provide an IPv6 address. In such cases it might also be needed to specify the network adapter, like `%eth0`. This seems to be the case for `ssh`, but not for `ping`, so you'd have to check if you need this.

## Steps to Reproduce

1. Download k3sup
2. Run `k3sup install --context --user --ip ` (with everything between <> filled in ofc.)

## Your Environment

* k3sup version:

```
0.12.12
```

* What Kubernetes distribution, client and server version are you using?

```
N/A
```

* What OS or type or VM are you using for your cluster? Where is it hosted? (for `k3sup install/join`):

* Operating System and version (e.g. Linux, Windows, MacOS):

```
Self-hosted.
Host OS: Windows 11 22H2 (build: 22621.963), using Hyper-V (Configuration version: 11.0) + multipass (for creating the VMs)

VM OS instances:
Linux 5.15.0-56-generic #62-Ubuntu SMP Tue Nov 22 19:54:14 UTC 2022 x86_64 x86_64 x86_64 GNU/Linux

PRETTY_NAME="Ubuntu 22.04.1 LTS"
NAME="Ubuntu"
VERSION_ID="22.04"
VERSION="22.04.1 LTS (Jammy Jellyfish)"
VERSION_CODENAME=jammy
ID=ubuntu
ID_LIKE=debian
HOME_URL="https://www.ubuntu.com/"
SUPPORT_URL="https://help.ubuntu.com/"
BUG_REPORT_URL="https://bugs.launchpad.net/ubuntu/"
PRIVACY_POLICY_URL="https://www.ubuntu.com/legal/terms-and-policies/privacy-policy"
UBUNTU_CODENAME=jammy
```

## Do you want to work on this?

Subject to design approval, are you willing to work on a Pull Request for this issue or feature request?

```
I would be willing, but I don't have very much experience with GoLang.
```