docs: clarify nodejs16 requirement + fix command (#1152)

Author: dreamorosi

Diff for: CONTRIBUTING.md

@@ -77,6 +77,9 @@ The following tools need to be installed on your system prior to starting workin
 
 First, [fork](https://docs.github.com/en/get-started/quickstart/fork-a-repo) the repository, and then run the following commands to clone and initialize the repository locally.
 
+> **Note**
+> In order for the commands below to work you need Node.js `16.x` and npm `8.x`
+
 ```console
 git clone https://github.com/{your-account}/aws-lambda-powertools-typescript.git
 cd aws-lambda-powertools-typescript

Diff for: package.json

@@ -15,7 +15,7 @@
     "test": "npm t -ws",
     "commit": "commit",
     "package": "npm run package",
-    "setup-local": "npm ci --foreground-scripts && cd examples/cdk && npm ci && cd ../../examples/sam && npm ci && cd ../../layer-publisher && npm ci && cd ../.. && npm run init-environment",
+    "setup-local": "export PROJECT_ROOT=$(pwd) && npm ci --foreground-scripts && cd $PROJECT_ROOT/examples/cdk && npm ci && cd $PROJECT_ROOT/examples/sam && npm ci && cd $PROJECT_ROOT/layer-publisher && npm ci && cd $PROJECT_ROOT/ && npm run init-environment",
     "build": "npm run build -ws",
     "postversion": "git push && git push --tags",
     "docs-website-build-run": "npm run docs-buildDockerImage && npm run docs-runLocalDocker",