Link to demo in readme

README.md

@@ -1,3 +1,7 @@
 # sb3.js
 
-**sb3.js** is a very experimental lightweight Scratch runtime based around generator functions.
+**sb3.js** is a very experimental lightweight Scratch runtime based around generator functions.
+
+It should currently be able to run many projects--those that use various extensions may or may not work.
+
+[Try out the demo!](https://valadaptive.github.io/sb3-js/demo.html)

demo.html

@@ -21,7 +21,7 @@
         <div class="load-project-controls">
             <input type="file" id="file-input" accept=".sb3">
             <div class="id-input">
-                <input id="id-textbox" type="text" placeholder="Enter a project ID...">
+                <input id="id-textbox" type="text" placeholder="Enter a project ID or URL">
                 <button id="id-button">Load project</button>
             </div>
         </div>