Add pnpm support

Author: dr460nf1r3

.gitignore

@@ -8,3 +8,4 @@
 /pkg/
 !vendor/**
 build
+node_modules

fixtures/pnpm/dev_deps/package.json

@@ -0,0 +1,13 @@
+{
+  "name": "dev-deps-pnpm",
+  "version": "1.0.0",
+  "dependencies": {
+    "lodash": "^4.17.21"
+  },
+  "devDependencies": {
+    "cookie": "0.4.1"
+  },
+  "engines": {
+    "node": "22.x"
+  }
+}

fixtures/pnpm/dev_deps/pnpm-lock.yaml

@@ -0,0 +1,14 @@
+{
+    "name": "node_web_app_with_pnpm",
+    "version": "1.0.0",
+    "main": "server.js",
+    "author": "CF Buildpacks Team",
+    "dependencies": {
+        "logfmt": "^1.4.0",
+        "express": "^5.2.1"
+    },
+    "engines": {
+        "node": "22.x",
+        "pnpm": "*"
+    }
+}