test: Add E2E test

test/e2e.sh

@@ -0,0 +1,19 @@
+#!/bin/bash
+
+set -e
+
+scriptDir=$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)
+
+if ! command -v pmg &> /dev/null; then
+    alias pmg="$scriptDir/../bin/pmg"
+fi
+
+echo "Running e2e tests..."
+
+## All these should be successful
+pmg npm install express --dry-run
+pmg --dry-run npm install express
+pmg --dry-run pnpm add express
+
+## All these should fail
+pmg --dry-run npm install nyc-config@10.0.0