add readme

workflow-steps/install-node/README.md

@@ -0,0 +1,30 @@
+## Usage
+
+```yaml
+- name: Install Node
+  uses: 'nrwl/nx-cloud-workflows/v4/workflow-steps/install-node/main.yaml'
+  inputs:
+    node_version: '20'
+```
+
+### Options
+
+#### node_version
+
+The node version to be installed. Any valid [nvm](https://github.com/nvm-sh/nvm/blob/master/README.md#usage) version is accepted.
+This input is optional, as the step will also check for a `.nvmrc` file in the root of the repository.
+If the file is present, the step will install the version specified in the file.
+If the file is not present, the step will not install any node version and leave the default installed node version on the image for subsequent steps
+
+For those using `volta`, the `volta.node` field in the `package.json` will also be picked up and used if present.
+
+The current order of precedence is:
+
+1. `node_version` input
+1. `.nvmrc` file
+1. `volta.node` field in `package.json`
+
+For example:
+
+- Install a specific node version: `node_version: '20.11.1'`
+- Install latest of major node version: `node_version: '20'`