[Carbon X] Toggle colors are inaccessible for g90 and g100 themes

Detailed description

The Carbon X Toggle component is inaccessible when someone uses the g90 or g100 themes provided by @carbon/themes

Here are a few screenshots with the g100 theme:

Looks like the issue is related to tokens, like this one here: https://github.com/IBM/carbon-components/blob/master/src/components/toggle/_toggle.scss#L272

// Toggle circle
&:after {
  background-color: $ui-02;
  ...
}

The $ui-02 color token is gray70 for g90 and gray80 for g100 themes (see: https://carbon-elements.netlify.com/themes/examples/preview/), which makes the toggle’s circle invisible when toggled off/deselected.

[jendowns]

@shixiedesign no worries at all! The only way I’m able to keep these tokens straight is by constantly looking at the theme preview site: https://carbon-elements.netlify.com/themes/examples/preview/ 😆 I appreciate your help with this 🙏

[jendowns]

Sure thing @shixiedesign! Are you able to assign this issue to me? I can get a PR together 👍

EDIT: first step is to add $icon-03 token to @carbon/themes & then I will follow up here to update the Toggle experimental theme.