chore: add design-tokens package to README and dependency graph (#168)

## **Description**

This PR updates the `README.md` to include the `design-tokens` package.
Additionally, the dependency graph in the README is regenerated by
running `yarn update-readme-content`, ensuring the new package is
accurately reflected.

[Follows migration
steps](https://github.com/MetaMask/metamask-design-system/blob/main/docs/package-migration-process-guide.md)

<img width="1108" alt="Screenshot 2024-11-27 at 11 06 04 AM"
src="https://github.com/user-attachments/assets/fa9e7b4d-0e17-4e81-9ffa-12c572cc1eda">

## **Related Issues**

Fixes: N/A

## **Manual Testing Steps**

1. Pull the branch and run `yarn update-readme-content` locally.
2. Verify that the `design-tokens` package is listed under the packages
section of the `README.md`.
3. Confirm that the dependency graph is updated to include the new
package.

## **Screenshots/Recordings**

### **Before**

*Current README content and dependency graph.*

<img width="616" alt="Screenshot 2024-11-27 at 11 00 56 AM"
src="https://github.com/user-attachments/assets/4dd808e2-2fce-4014-a8b6-1a7dad1522e1">


### **After**

*Updated README content reflecting the new package.*

<img width="633" alt="Screenshot 2024-11-27 at 11 00 33 AM"
src="https://github.com/user-attachments/assets/0658d012-83f0-4a58-88c1-30384fb83fab">


## **Pre-merge Author Checklist**

- [x] Followed [[MetaMask Contributor
Docs](https://github.com/MetaMask/contributor-docs)](https://github.com/MetaMask/contributor-docs).
- [x] Completed the PR template to the best of my ability.
- [x] Verified updates with `yarn update-readme-content`.
- [x] Included any necessary tests or documentation updates.
- [x] Applied appropriate labels based on [[labeling
guidelines](https://github.com/MetaMask/metamask-extension/blob/develop/.github/guidelines/LABELING_GUIDELINES.md)](https://github.com/MetaMask/metamask-extension/blob/develop/.github/guidelines/LABELING_GUIDELINES.md).

## **Pre-merge Reviewer Checklist**

- [ ] Confirmed updates to `README.md` and dependency graph.
- [ ] Verified manual testing steps and confirmed changes work as
intended.
- [ ] Reviewed code or documentation updates for clarity and
completeness.

README.md

@@ -12,6 +12,7 @@ This repository contains the following packages [^fn1]:
 - [`@metamask/design-system-react-native`](packages/design-system-react-native)
 - [`@metamask/design-system-tailwind-preset`](packages/design-system-tailwind-preset)
 - [`@metamask/design-system-twrnc-preset`](packages/design-system-twrnc-preset)
+- [`@metamask/design-tokens`](packages/design-tokens)
 
 <!-- end package list -->
 
@@ -27,7 +28,9 @@ linkStyle default opacity:0.5
   design_system_react_native(["@metamask/design-system-react-native"]);
   design_system_tailwind_preset(["@metamask/design-system-tailwind-preset"]);
   design_system_twrnc_preset(["@metamask/design-system-twrnc-preset"]);
+  design_tokens(["@metamask/design-tokens"]);
   design_system_react --> design_system_tailwind_preset;
+  design_system_react_native --> design_system_twrnc_preset;
 ```
 
 <!-- end dependency graph -->