imp: improve code samples to make them work on firefox

src/samples.js

@@ -1,4 +1,20 @@
 const HELLO_WORLD = `class HelloWorld extends owl.core.Component {
+  constructor(...args) {
+    super(...args);
+    this.inlineTemplate = \`<div>Hello <t t-esc="props.name"/></div>\`;
+  }
+}
+
+const env = {
+    qweb: new owl.core.QWeb()
+};
+
+const hello = new HelloWorld(env, { name: "World" });
+hello.mount(document.body);
+`;
+
+const HELLO_WORLD_ESNEXT = `// This example will not work if your browser does not support ESNext Class Fields
+class HelloWorld extends owl.core.Component {
   inlineTemplate = \`<div>Hello <t t-esc="props.name"/></div>\`;
 }
 
@@ -11,15 +27,15 @@ hello.mount(document.body);
 `;
 
 const WIDGET_COMPOSITION = `class Counter extends owl.core.Component {
-  inlineTemplate = \`
-    <div>
-      <button t-on-click="increment(-1)">-</button>
-      <span style="font-weight:bold">Value: <t t-esc="state.value"/></span>
-      <button t-on-click="increment(1)">+</button>
-    </div>\`;
 
   constructor(parent, props) {
     super(parent, props);
+    this.inlineTemplate = \`
+      <div>
+        <button t-on-click="increment(-1)">-</button>
+        <span style="font-weight:bold">Value: <t t-esc="state.value"/></span>
+        <button t-on-click="increment(1)">+</button>
+      </div>\`;
     this.state = {
       value: props.initialState || 0
     };
@@ -31,13 +47,17 @@ const WIDGET_COMPOSITION = `class Counter extends owl.core.Component {
 }
 
 class App extends owl.core.Component {
-  inlineTemplate = \`
-    <div>
-        <t t-widget="Counter" t-props="{initialState: 1}"/>
-        <t t-widget="Counter" t-props="{initialState: 42}"/>
-    </div>\`;
 
-  widgets = { Counter };
+  constructor(...args) {
+    super(...args);
+    this.inlineTemplate = \`
+      <div>
+          <t t-widget="Counter" t-props="{initialState: 1}"/>
+          <t t-widget="Counter" t-props="{initialState: 42}"/>
+      </div>\`;
+    this.widgets = { Counter };
+  }
+
 }
 
 const env = {
@@ -58,6 +78,10 @@ export const SAMPLES = [
     description: "Hello World",
     code: HELLO_WORLD
   },
+  {
+    description: "Hello World (ESNext)",
+    code: HELLO_WORLD_ESNEXT
+  },
   {
     description: "Widget Composition",
     code: WIDGET_COMPOSITION