[IMP] playground: slightly improve default text

tools/playground/playground.css

@@ -173,8 +173,10 @@ body {
 }
 
 .right-pane .note {
-  font-size: 20px;
+  font-size: 18px;
+  text-align: left;
   margin-top: 20px;
+  padding: 5%;
 }
 
 .right-pane .error {

tools/playground/samples.js

@@ -5,7 +5,7 @@ class Greeter extends Component {
     state = useState({ word: 'Hello' });
 
     toggle() {
-        this.state.word = this.state.word === 'Hi' ? 'Hello' : 'Hi'
+        this.state.word = this.state.word === 'Hi' ? 'Hello' : 'Hi';
     }
 }
 

tools/playground/templates.xml

@@ -45,7 +45,11 @@
           <div>🦉 Odoo Web Library 🦉</div>
           <div>v<t t-esc="version"/></div>
           <div class="url"><a href="https://github.com/odoo/owl">https://github.com/odoo/owl</a></div>
-          <div class="note">Note: these examples require a recent browser to work without a transpilation step. </div>
+          <div class="note">
+            <p>Note: these examples are using recent features of Javascript, and require a recent browser to work without a transpilation step!
+              For example, it makes use of class fields and class static fields. These examples should work in a recent Chrome version.
+            </p>
+          </div>
         </div>
         <div t-if="state.error" class="error">
           <h3>Error</h3>