Provide short instructions for Yarn Berry use (#801)

Co-authored-by: Zach Bloomquist <github@chary.us>

README.md

@@ -1146,6 +1146,14 @@ Name | Description
 
 This action installs local dependencies using lock files. If `yarn.lock` file is found, the install uses `yarn --frozen-lockfile` command. Otherwise it expects to find `package-lock.json` and install using `npm ci` command.
 
+The above default `yarn` installation command can be replaced for [Yarn Berry](https://yarnpkg.com/) (Yarn 2 and later) using the `install-command` parameter, for example:
+
+```yml
+- uses: cypress-io/github-action@v5
+  with:
+    install-command: yarn install
+```
+
 This action uses several production dependencies. The minimum Node version required to run this action depends on the minimum Node required by the dependencies.
 
 ## Debugging