Extracted esbuild config to a build script

Allows us to use NodeJS code for file/directory locating to not be
shell/os specific, while also also reducing duplicated complexity within
packages.json file.

Related to #3323

dev/build/esbuild.js

@@ -0,0 +1,32 @@
+#!/usr/bin/env node
+
+const esbuild = require('esbuild');
+const fs = require('fs');
+const path = require('path');
+
+// Check if we're building for production
+// (Set via passing `production` as first argument)
+const isProd = process.argv[2] === 'production';
+
+// Gather our input files
+const jsInDir = path.join(__dirname, '../../resources/js');
+const jsInDirFiles = fs.readdirSync(jsInDir, 'utf8');
+const entryFiles = jsInDirFiles
+    .filter(f => f.endsWith('.js') || f.endsWith('.mjs'))
+    .map(f => path.join(jsInDir, f));
+
+// Locate our output directory
+const outDir = path.join(__dirname, '../../public/dist');
+
+// Build via esbuild
+esbuild.build({
+    bundle: true,
+    entryPoints: entryFiles,
+    outdir: outDir,
+    sourcemap: true,
+    target: 'es2020',
+    mainFields: ['module', 'main'],
+    format: 'esm',
+    minify: isProd,
+    logLevel: "info",
+}).catch(() => process.exit(1));