validation documentation not updated for aurelia-webpack

**I'm submitting a bug report**
The doc is not updated

**Expected/desired behavior:**
[here](https://aurelia.io/docs/plugins/validation#introduction) at the beginning in the Introduction section, the documentation should say to use `.plugin(PLATFORM.moduleName('aurelia-validation'))` instead of `.plugin('aurelia-validation')` as noted [here](https://github.com/aurelia/webpack-plugin/issues/99#issuecomment-290034760).

Cheers

Start at the linked Aurelia validation documentation's Introduction section and compare its plugin example with the referenced aurelia-webpack guidance. Done means the example uses `.plugin(PLATFORM.moduleName('aurelia-validation'))` instead of `.plugin('aurelia-validation')`.

Written by the indexing model from the issue text.