Update progress bar component to accept custom color indicator

[orion-cengage]

Purpose: Allow consumers to change the indicator of the progress bar to any custom color they want, in addition to our presets.

AC

• Allow consumer to use a string like "#B12FAD" to set the color of the indicator.
• Make sure the track can still not be changed.
• How can we handle allowing a different color set when Inversed?

[silvalaura]

Make a note in the docs site that, when using custom colors, they must be checked for color contrast for a11y.

[silvalaura]

Create an example that swaps between using chartColorsInverse and chartColors depending on whether the ProgressBar is using inverse.

[orion-cengage]

QA complete - Update to progress bar and documentation looks great.

[chris-cedrone-cengage]

Looks good here!