Document the use of babel transform-class-properties to export classes with static properties using stealjs

[piraz]

It would be great to have documented the babel configuration to use the transform-class-properties plugin on Can 6 documentation to export classes with static properties using steal.

If we don't use the configuration an error like this will be displayed when I execute steal-tools export:

{ SyntaxError: unknown: Missing class properties transform.
   5 | 
   6 | export default class FazAlert extends StacheElement {
>  7 |     static view = alertTemplate;
     |     ^
   8 | 
   9 |     static get props() {
  10 |         return {

Using this configuration on my package.json fixes the issue:

"steal": {
    "plugins": [
      "steal-stache"
    ],
    "babelOptions": {
      "plugins": [
        "transform-class-properties" // <==== This one, right here
      ]
    }
  }

[cherifGsoul]

@piraz thank you for reporting this, using transform-class-properties is already documented in StealJS section https://canjs.com/doc/guides/setup.html#StealJS.

Feel free to open the issue if you find that the section needs to be improved.

[cherifGsoul]

After seeing slack discussion, @piraz suggested to add it to add it to migrating to CanJS 6 docs.