Update and rename README.md to Github.help/Setup-node

Github.help/Setup-node

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+# setup-node
+
+<p align="left">
+  <a href="https://github.com/actions/setup-node/actions?query=workflow%3Abuild-test"><img alt="build-test status" src="https://github.com/actions/setup-node/workflows/build-test/badge.svg"></a> <a href="https://github.com/actions/setup-node/actions?query=workflow%3Aversions"><img alt="versions status" src="https://github.com/actions/setup-node/workflows/versions/badge.svg"></a> <a href="https://github.com/actions/setup-node/actions?query=workflow%3Aproxy"><img alt="proxy status" src="https://github.com/actions/setup-node/workflows/proxy/badge.svg"></a> 
+</p>
+
+This action provides the following functionality for GitHub Actions users:
+
+- Optionally downloading and caching distribution of the requested Node.js version, and adding it to the PATH
+- Optionally caching npm/yarn/pnpm dependencies
+- Registering problem matchers for error output
+- Configuring authentication for GPR
+# Usage
+
+See [action.yml](action.yml)
+
+**Basic:**
+```yaml
+steps:
+- uses: actions/checkout@v2
+- uses: actions/setup-node@v2
+  with:
+    node-version: '14'
+- run: npm install
+- run: npm test
+```
+
+The `node-version` input is optional. If not supplied, the node version from PATH will be used. However, it is recommended to always specify Node.js version and don't rely on the system one.  
+
+The action will first check the local cache for a semver match. If unable to find a specific version in the cache, the action will attempt to download a version of Node.js. It will pull LTS versions from [node-versions releases](https://github.com/actions/node-versions/releases) and on miss or failure will fall back to the previous behavior of downloading directly from [node dist](https://nodejs.org/dist/).
+
+For information regarding locally cached versions of Node.js on GitHub hosted runners, check out [GitHub Actions Virtual Environments](https://github.com/actions/virtual-environments).
+
+#### Supported version syntax
+The `node-version` input supports the following syntax:
+
+major versions: `12`, `14`, `16`  
+more specific versions: `10.15`, `14.2.0`, `16.3.0`  
+nvm lts syntax: `lts/erbium`, `lts/fermium`, `lts/*`  
+
+## Caching packages dependencies
+
+The action has a built-in functionality for caching and restoring dependencies. It uses [actions/cache](https://github.com/actions/cache) under the hood for caching dependencies but requires less configuration settings. Supported package managers are `npm`, `yarn`, `pnpm` (v6.10+). The `cache` input is optional, and caching is turned off by default.
+
+The action defaults to search for the dependency file (`package-lock.json` or `yarn.lock`) in the repository root, and uses its hash as a part of the cache key. Use `cache-dependency-path` for cases when multiple dependency files are used, or they are located in different subdirectories.
+
+See the examples of using cache for `yarn` / `pnpm` and  `cache-dependency-path` input in the [Advanced usage](docs/advanced-usage.md#caching-packages-dependencies) guide.
+
+**Caching npm dependencies:**
+```yaml
+steps:
+- uses: actions/checkout@v2
+- uses: actions/setup-node@v2
+  with:
+    node-version: '14'
+    cache: 'npm'
+- run: npm install
+- run: npm test
+```
+
+**Caching npm dependencies in monorepos:**
+```yaml
+steps:
+- uses: actions/checkout@v2
+- uses: actions/setup-node@v2
+  with:
+    node-version: '14'
+    cache: 'npm'
+    cache-dependency-path: subdir/package-lock.json
+- run: npm install
+- run: npm test
+```
+
+## Matrix Testing:
+```yaml
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        node: [ '12', '14', '16' ]
+    name: Node ${{ matrix.node }} sample
+    steps:
+      - uses: actions/checkout@v2
+      - name: Setup node
+        uses: actions/setup-node@v2
+        with:
+          node-version: ${{ matrix.node }}
+      - run: npm install
+      - run: npm test
+```
+## Advanced usage
+
+1. [Check latest version](docs/advanced-usage.md#check-latest-version)
+2. [Using a node version file](docs/advanced-usage.md#node-version-file)
+3. [Using different architectures](docs/advanced-usage.md#architecture)
+4. [Caching packages dependencies](docs/advanced-usage.md#caching-packages-dependencies)
+5. [Using multiple operating systems and architectures](docs/advanced-usage.md#multiple-operating-systems-and-architectures)
+6. [Publishing to npmjs and GPR with npm](docs/advanced-usage.md#publish-to-npmjs-and-gpr-with-npm)
+7. [Publishing to npmjs and GPR with yarn](docs/advanced-usage.md#publish-to-npmjs-and-gpr-with-yarn)
+8. [Using private packages](docs/advanced-usage.md#use-private-packages)
+
+# License
+
+The scripts and documentation in this project are released under the [MIT License](LICENSE)
+
+# Contributions
+
+Contributions are welcome!  See [Contributor's Guide](docs/contributors.md)
+
+## Code of Conduct
+
+:wave: Be nice.  See [our code of conduct](CONDUCT)