High contrast support for charts

[mcoker]

CSS changes needed to support patternfly/patternfly-react#12053

[mcoker]

@lboehling I just pulled the latest tokens from the design tokens figma and am not seeing the new chart area opacity token. I put up a PR in the design token repo from the latest tokens (patternfly/design-tokens#118) and don't see it listed and don't see it in the existing tokens-charts.scss file. Can you verify it's in figma or if I should get it from somewhere else?

[lboehling]

@mcoker are you pulling from the main pf6 design tokens library or from the high contrast file? I haven't ported over the chart HC tokens to the main design tokens file yet -- I wanted to validate them first before adding and exposing those HC modes/values in our published libraries. The opacity token is showing for me.

[mcoker]

@lboehling ah nope, I was pulling from the wrong file. Thank you! Put up a new design tokens PR - patternfly/design-tokens#119. Can you review that when you get a chance? Once that's approved, I can pull them into core and make the charts updates.