Guard against npx without set-script

Fixes #35, #38

Author: David Heinemeier Hansson

lib/install/esbuild/install.rb

@@ -2,4 +2,10 @@
 run "yarn add esbuild"
 
 say "Add build script"
-run %(npm set-script build "esbuild app/javascript/*.* --bundle --outdir=app/assets/builds")
+build_script = "esbuild app/javascript/*.* --bundle --outdir=app/assets/builds"
+
+if (`npx -v`.to_f < 7.1 rescue "Missing")
+  say %(Add "scripts": { "build": "#{build_script}" to your package.json), :green
+else
+  run %(npm set-script build "#{build_script}")
+end

lib/install/rollup/install.rb

@@ -3,4 +3,10 @@
 run "yarn add rollup @rollup/plugin-node-resolve"
 
 say "Add build script"
-run %(npm set-script build "rollup -c rollup.config.js")
+build_script = "rollup -c rollup.config.js"
+
+if (`npx -v`.to_f < 7.1 rescue "Missing")
+  say %(Add "scripts": { "build": "#{build_script}" to your package.json), :green
+else
+  run %(npm set-script build "#{build_script}")
+end

lib/install/webpack/install.rb

@@ -3,4 +3,10 @@
 run "yarn add webpack webpack-cli"
 
 say "Add build script"
-run %(npm set-script build "webpack --config webpack.config.js")
+build_script = "webpack --config webpack.config.js"
+
+if (`npx -v`.to_f < 7.1 rescue "Missing")
+  say %(Add "scripts": { "build": "#{build_script}" to your package.json), :green
+else
+  run %(npm set-script build "#{build_script}")
+end