refactor: replace shell scripts with JS for cross-platform support (#875)

Convert bin/ shell scripts to Node.js and npm scripts using shx and npm-run-all2. Remove unused build-icons.sh. Inlined simple scripts (build-docs-liquid, build-apidoc) as npm scripts.

Made-with: Cursor

bin/perf-diff.js

@@ -0,0 +1,17 @@
+const { execSync } = require('child_process')
+const fs = require('fs')
+const path = require('path')
+
+const root = path.resolve(__dirname, '..')
+const version = require(path.join(root, 'package.json')).version
+
+const fileLocal = path.join(root, 'dist/liquid.node.js')
+const fileLatest = path.join(root, `dist/liquid.node.${version}.js`)
+
+if (!fs.existsSync(fileLatest)) {
+  const url = `https://unpkg.com/liquidjs@${version}/dist/liquid.node.js`
+  console.log(`Downloading liquidjs@${version}...`)
+  execSync(`curl -sL -o "${fileLatest}" "${url}"`)
+}
+
+execSync(`node benchmark/diff.js "${fileLocal}" "${fileLatest}"`, { cwd: root, stdio: 'inherit' })