feat(tokens): add design tokens architecture (#29245)

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## What is the new behavior?
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Following the Design Doc for the new Ionic Design System, an
architecture for Design Tokens was added.

1. Added new `foundations` folder inside the `src`, to hold all the
tokens related files.
2. On this file, a json with all the tokens for the new Design System
was added. The format followed was the one suggested on the [W3C
draft](https://design-tokens.github.io/community-group/format/).
3. Added a dev dependency for [Styles
Dictionary](https://amzn.github.io/style-dictionary/#/), version 3.9.2.
4. Added a tokens.js script that will take care of transforming the json
tokens into the desired output. For now, three files are being
generated: ionic.vars.css (:root with all CSS Variables); ionic.vars.css
(scss variables for each token) and ionic.utility.css (a new
utility-class for each token)
5. Added the script `npm run build.tokens` to package.json, that will
generate the three files mentioned above.

For now, all these changes bring no impact to the rest of the Framework,
as these variables are not yet being consumed.

The `margin`, `padding` and `border-radius` were removed from the
prohibited properties on lint, to prevent lint errors with the new
utility-classes. This is very open to discussion/feedback if it's seen
as not ok.

The `build` command now includes the `build.tokens` script, to make sure
the files are always generated, in case someone forget to run the
command, after changing the json file!

## Does this introduce a breaking change?

- [ ] Yes
- [x] No

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Co-authored-by: Sean Perkins <13732623+sean-perkins@users.noreply.github.com>