Requirement to run with elevated privileges on Mac/Windows should come before command usage in README

[zrisher]

I struggled getting this to work for a while until I scrolled down to the bottom of the README and saw specific instructions to run the command with elevated permissions if using Windows or MacOS.

IMHO, a note about this requirement should be placed closer to the first instructions using the commands. E.g.:

## How to use it

Run a KIND cluster...

**Note**

Control-plane nodes need to remove ...

+ **Note**
+ Windows and Mac users must provide elevated privileges when running the below commands. See [Mac and Windows Support](#mac-and-windows-support).
+

Once the cluster is running, we need to run the `cloud-provider-kind` in a terminal and keep it running...

I think this would save other users some time.

If this change is welcome, let me know and I'll be happy to provide a PR.

[aojea]

We may have a note in the install section to reference the windows and mac section