chore: improve dev script so output can be meaningfully watched

This makes it work well in VS Code (f.e. it will use $ts-watch mode to read errors from stdout and display them in the "PROBLEMS" pane).

Plus this tells newcomers how to quickly get things started in dev mode (watch mode) for easy dev cycles.

package.json

@@ -25,6 +25,7 @@
 	],
 	"dependencies": {},
 	"scripts": {
+		"dev": "(npm run tsc-watch -- --preserveWatchOutput & p1=$!; npm run rollup-build -- --watch & p2=$!; wait $p1 $p2)",
 		"build": "rimraf dist .tmp && node scripts/write-version.js && npm run tsc && npm run rollup-build",
 		"rollup-build": "rollup -c ./rollup.config.js",
 		"tsc": "tsc",

rollup.config.js

@@ -5,28 +5,34 @@ export default [
 		input: '.tmp/Index.js',
 		// https://github.com/rollup/rollup/wiki/Troubleshooting#this-is-undefined
 		context: 'this',
+		watch: {clearScreen: false},
 		output: [
 			{
 				file: 'dist/tween.umd.js',
 				name: 'TWEEN',
 				format: 'umd',
+				exports: 'named',
 			},
 			{
 				file: 'dist/tween.amd.js',
 				format: 'amd',
+				exports: 'named',
 			},
 			{
 				file: 'dist/tween.cjs.js',
 				format: 'cjs',
+				exports: 'named',
 			},
 			{
 				file: 'dist/tween.esm.js',
 				format: 'es',
+				exports: 'named',
 			},
 		],
 	},
 	{
 		input: './.tmp/Index.d.ts',
+		watch: {clearScreen: false},
 		output: [{file: 'dist/tween.d.ts', format: 'es'}],
 		plugins: [dts()],
 	},