refactor(index.js,-readme,-packagejson): require both placeholder and include options

BREAKING CHANGE: both include and placeholder config options are required

Author: mcha

README.md

@@ -9,13 +9,33 @@ export default {
     dir: 'dist',
   },
   plugins: [
-    litTw({ include: 'src/components/**/*.ts' }),
+    litTw({
+      include: 'src/components/**/*.ts',
+      placeholder: 'tw_placeholder',
+    }),
   ],
-}
+};
 ```
 
+lit component
+
+```ts
+import { html, css, LitElement } from 'lit';
+import { customElement } from 'lit/decorators.js';
+
+@customElement('simple-component')
+export class SimpleComponent extends LitElement {
+  static styles = css`tw_placeholder`;
+
+  render() {
+    return html`<h1 class="text-purple-400 hover_text-green-500">Hello, world!</h1>`;
+  }
+}
+```
 
 ## Todos
-- is this performant?
-- tw seperator slash read tailwind config, styles.css?
-- ...
+
+- is this performant???
+- tailwind separator (`_` to default one `:`)
+- read tailwind config, styles.css?
+- ...

helpers/index.js

@@ -0,0 +1,17 @@
+// https://github.com/rollup/plugins/blob/master/util/test.js
+const getCode = async (bundle, outputOptions, allFiles = false) => {
+  const { output } = await bundle.generate(
+    outputOptions || { format: 'iife' },
+  );
+  if (allFiles) {
+    return output.map(({ code, fileName, source, map }) => {
+      return { code, fileName, source, map };
+    });
+  }
+  const [{ code }] = output;
+  return code;
+};
+
+module.exports = {
+  getCode,
+};