chore: Filter ‘default’ suffix from CSS custom properties and Sass / JS variables

[alimpens]

Describe the pull request

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What

This filters the 'default' suffix from CSS custom properties and Sass / JS variables when generating our tokens.
So ams.color.default becomes --ams-color and amsColor.

Why

We're remodelling our brand and common tokens, and because of how JSON works, we need to use 'default' a lot.
This isn't necessary for tokens though, so this change filters that out.

How

By adding custom transform functions to our Style Dictionary build.

Checklist

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• Add or update unit tests
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