ENG-219: Target Node 20 instead of Node 24

Node 20 strikes a better balance for compatibility. It's the version
used by WordPress's Gutenberg project and is currently the default on
GitHub-hosted runners, so users with strict engine checking enabled in
.npmrc should be able to install without issues.

Author: d4mation

.nvmrc

@@ -1 +1 @@
-24
+20

package.json

@@ -7,7 +7,7 @@
   },
   "type": "module",
   "engines": {
-    "node": ">=24"
+    "node": ">=20"
   },
   "files": [
     "dist/",

tsdown.config.ts

@@ -3,7 +3,7 @@ import { defineConfig } from 'tsdown';
 export default defineConfig({
   entry: ['src/cli.ts'],
   format: ['esm'],
-  target: 'node24',
+  target: 'node20',
   outDir: 'dist',
   fixedExtension: false,
   sourcemap: true,