Add a Motivation and Background section (#26)

This adds a Motivation and Background section that leverages the contents
of the WebGPU Explainer and links to it for further details.

The update also moves the definition of "GPU" from the Scope section to that
new section.

wg-charter.html

@@ -52,6 +52,7 @@
     <header id="header">
       <aside>
         <ul id="navbar">
+          <li><a href="#background">Background</a></li>
           <li><a href="#scope">Scope</a></li>
           <li><a href="#deliverables">Deliverables</a></li>
           <li><a href="#success-criteria">Success criteria</a></li>
@@ -142,16 +143,27 @@ <h1 id="title"><i class="todo">PROPOSED</i> GPU for the Web Working Group Charte
         </table>
       </section>
 
-
-
-      <section id="scope" class="scope">
-        <h2>Scope</h2>
+      <section id="background" class="background">
+        <h2>Motivation and Background</h2>
+        <p>
+          In this document, the term <dfn>GPU</dfn> stands for Graphics Processing Unit, typically a piece of hardware dedicated to efficiently processing graphics and related features.
+        </p>
+        <p>
+          GPUs have become essential for drawing complex images efficiently, including for rendering virtual reality and augmented reality scenes in real-time as needed by the <a href="https://www.w3.org/TR/webxr/">WebXR Device API</a>. GPUs are also at the heart of computations that leverage parallelism, such as machine learning inference.
+        </p>
         <p>
-            In this document, the term <dfn>GPU</dfn> stands for Graphics
-            Processing Unit, typically a piece of hardware dedicated to
-            efficiently processing graphics and related features.
+          Web applications may leverage GPUs through the <a href="https://www.khronos.org/webgl/">WebGL</a> family of APIs, but WebGL does not enable access to more advanced features of GPUs, focuses on drawing images and does not provide first-class support for performing general computations, and is not agnostic of the GPU system API exposed by the underlying operating system.
         </p>
+        <p>
+          The overall goal of the GPU for the Web Working Group is to provide a foundation that can be implemented on top of modern GPU system APIs to expose modern GPU functionality on the Web, both for computation and for image rendering.
+        </p>
+        <p>
+          See also the <a href="https://gpuweb.github.io/gpuweb/explainer/">WebGPU Explainer</a>, maintained by the GPU for the Web Community Group, for additional background, use cases, and design considerations.
+        </p>
+      </section>
 
+      <section id="scope" class="scope">
+        <h2>Scope</h2>
         <p>
             This Working Group will recommend a Web programming interface for
             graphics and computation that:
@@ -480,6 +492,7 @@ <h3>
                   <li>Add link to Conformance Test Suite</li>
                   <li>Switch to CR with Snapshots (no intent to advance to Recommendation) mode</li>
                   <li>Clarify that technical discussions on the deliverables are now driven by this Working Group</li>
+                  <li>Add a Motivation and Background section</li>
                 </ul></td>
               </tr>
             </tbody>