Configure npm proxy when proxy environmentals exist (#712)

src/node/devcontainer-feature.json

 {
     "id": "node",
-    "version": "1.3.0",
+    "version": "1.3.1",
     "name": "Node.js (via nvm), yarn and pnpm",
     "documentationURL": "https://github.com/devcontainers/features/tree/main/src/node",
     "description": "Installs Node.js, nvm, yarn, pnpm, and needed dependencies.",

src/node/install.sh

@@ -228,6 +228,9 @@ if type pnpm > /dev/null 2>&1; then
     echo "pnpm already installed."
 else
     if type npm > /dev/null 2>&1; then
+        [ ! -z "$http_proxy" ] && npm set proxy="$http_proxy"
+        [ ! -z "$https_proxy" ] && npm set https-proxy="$https_proxy"
+        [ ! -z "$no_proxy" ] && npm set noproxy="$no_proxy"
         npm install -g pnpm
     else
         echo "Skip installing pnpm because npm is missing"