Update preview build documentation (MetaMask#1296)

README.md

@@ -30,12 +30,31 @@ When developing changes to packages within this repository that a different proj
 If you're a MetaMask contributor, you can create these preview versions via draft pull requests:
 
 1. Navigate to your settings within GitHub and [create a classic access token](https://docs.github.com/en/authentication/keeping-your-account-and-data-secure/creating-a-personal-access-token#creating-a-personal-access-token-classic). Make sure to give this token the `packages:read` scope.
-2. Switch to your project locally and add a `.npmrc` file with the following content, filling in the appropriate areas:
-   ```
-   @metamask:registry=https://npm.pkg.github.com
-   //npm.pkg.github.com/:_authToken=<your personal access token>
-   ```
-   Make sure not to commit this file.
+2. Switch to your project locally and add/edit the appropriate file with the following content, filling in the appropriate areas:
+
+   - **Yarn 1 (classic) or NPM**
+
+     Add the following in `.npmrc`
+
+     ```
+     @metamask:registry=https://npm.pkg.github.com
+     //npm.pkg.github.com/:_authToken=<your personal access token>
+     ```
+
+   - **Yarn >= 2 (berry):**
+
+     Add the following in `.yarnrc.yml`
+
+     ```
+     npmScopes:
+        metamask:
+           npmAlwaysAuth: true
+           npmAuthToken: <your personal access token>
+           npmRegistryServer: 'https://npm.pkg.github.com'
+     ```
+
+   Make sure not to commit these changes.
+
 3. Go to GitHub and open up a pull request for this repository, then post a comment on the PR with the text `@metamaskbot publish-preview`. (This triggers the `publish-preview` GitHub action.)
 4. After a few minutes, you will see a new comment indicating that all packages have been published with the format `<package name>-<commit id>`.
 5. Switch back to your project locally and update `package.json` by replacing the versions for the packages you've changed in your PR using the new version format (e.g. `1.2.3-e2df9b4` instead of `~1.2.3`), then run `yarn install`.
@@ -46,12 +65,31 @@ If you're a MetaMask contributor, you can create these preview versions via draf
 If you're a contributor and you've forked this repository, you can create preview versions for a branch via provided scripts:
 
 1. Navigate to your settings within GitHub and [create a **classic** access token](https://docs.github.com/en/authentication/keeping-your-account-and-data-secure/creating-a-personal-access-token#creating-a-personal-access-token-classic). Make sure to give this token the `packages:read` scope.
-2. Switch to your project locally and add a `.npmrc` file with the following content, filling in the appropriate areas:
-   ```
-   @<your GitHub username>:registry=https://npm.pkg.github.com
-   //npm.pkg.github.com/:_authToken=<your personal access token>
-   ```
-   Make sure not to commit this file.
+2. Switch to your project locally and add/edit the appropriate file with the following content, filling in the appropriate areas.
+
+   - **Yarn 1 (classic) or NPM:**
+
+     Add the following in `.npmrc`
+
+     ```
+     @<your GitHub username>:registry=https://npm.pkg.github.com
+     //npm.pkg.github.com/:_authToken=<your personal access token>
+     ```
+
+   - **Yarn >= 2 (berry):**
+
+     Add the following in `.yarnrc.yml`
+
+     ```
+     npmScopes:
+        <your GitHub username>:
+           npmAlwaysAuth: true
+           npmAuthToken: <your personal access token>
+           npmRegistryServer: 'https://npm.pkg.github.com'
+     ```
+
+   Make sure not to commit these changes.
+
 3. Open the `package.json` for each package that you want to publish and change the scope in the name from `@metamask` to `@<your GitHub username>`.
 4. Switch to your fork of this repository locally and run `yarn prepare-preview-builds "$(git rev-parse --short HEAD)" && yarn build && yarn publish-previews` to generate preview versions for all packages based on the current branch and publish them to GitHub Package Registry. Take note of the version that is published; it should look like `1.2.3-e2df9b4` instead of `1.2.3`.
 5. Switch back to your project and update `package.json` by replacing the versions for all packages you've changed using the version that was output in the previous step, then run `yarn install`.