Switch paper-toggle-button to mwc-switch (#3683)

* Switch paper-toggle-button to mwc-switch

Closes https://github.com/home-assistant/home-assistant-polymer/issues/3352

* ha-switch

* apply not-checked theming

Thanks @bramkragten!

* address review comments

gallery/src/components/demo-cards.js

@@ -1,9 +1,9 @@
 import { html } from "@polymer/polymer/lib/utils/html-tag";
 import { PolymerElement } from "@polymer/polymer/polymer-element";
 import "@polymer/app-layout/app-toolbar/app-toolbar";
-import "@polymer/paper-toggle-button/paper-toggle-button";
 
 import "./demo-card";
+import "../../../src/components/ha-switch";
 
 class DemoCards extends PolymerElement {
   static get template() {
@@ -26,9 +26,7 @@ class DemoCards extends PolymerElement {
       </style>
       <app-toolbar>
         <div class="filters">
-          <paper-toggle-button checked="{{_showConfig}}"
-            >Show config</paper-toggle-button
-          >
+          <ha-switch checked="{{_showConfig}}">Show config</ha-switch>
         </div>
       </app-toolbar>
       <div class="cards">

gallery/src/components/demo-more-infos.js

@@ -1,9 +1,9 @@
 import { html } from "@polymer/polymer/lib/utils/html-tag";
 import { PolymerElement } from "@polymer/polymer/polymer-element";
 import "@polymer/app-layout/app-toolbar/app-toolbar";
-import "@polymer/paper-toggle-button/paper-toggle-button";
 
 import "./demo-more-info";
+import "../../../src/components/ha-switch";
 
 class DemoMoreInfos extends PolymerElement {
   static get template() {
@@ -26,9 +26,7 @@ class DemoMoreInfos extends PolymerElement {
       </style>
       <app-toolbar>
         <div class="filters">
-          <paper-toggle-button checked="{{_showConfig}}"
-            >Show entity</paper-toggle-button
-          >
+          <ha-switch checked="{{_showConfig}}">Show entity</ha-switch>
         </div>
       </app-toolbar>
       <div class="cards">