Add styling part

package.json

@@ -1,6 +1,6 @@
 {
   "name": "@tp/tp-color-picker",
-  "version": "1.1.0",
+  "version": "1.2.0",
   "description": "",
   "main": "tp-color-picker.js",
   "scripts": {

tp-color-picker.js

@@ -84,7 +84,7 @@ class TpColorPicker extends FormElement(DomQuery(LitElement)) {
     return html`
       <tp-popup id="popup" part="popup" @is-open-changed=${e => this.isOpen = e.detail}>
         <div slot="toggle" part="selection" style="${this._showPickedColor(this.value)}"></div>
-        <div slot="content" @click="${this._selectColor}">
+        <div slot="content" part="selector" @click="${this._selectColor}">
           <div class="wrap">
             ${this.colorList.map(color => html`
               <div color style="${this._bgColor(color)}"></div>