help: Add 3D Acceleration Page

Add user help documentation to enable 3D Acceleration for boxes; Update General tab
within the Properties View section within the interface page to add an entry for
3D acceleration.

Ref: #611

help/C/3d-acceleration.page

+<page xmlns="http://projectmallard.org/1.0/"
+      type="topic" style="task"
+      id="3d-acceleration">
+  <info>
+    <revision pkgversion="3.38.0" date="2020-10-04" status="review"/>
+    <link type="guide" xref="index#use" />
+
+    <credit type="author copyright">
+      <name>Pranali Deshmukh</name>
+      <email>pranali21293@gmail.com</email>
+      <years>2020</years>
+    </credit>
+
+    <include href="legal.xml" xmlns="http://www.w3.org/2001/XInclude"/>
+
+    <desc>Enable 3D Acceleration for your box.</desc>
+  </info>
+
+  <title>3D Acceleration</title>
+
+  <comment>
+    <cite date="2020-10-04" href="mailto:pranali21293@gmail.com">Pranali Deshmukh</cite>
+    <p>This assumes the reader has a basic understanding of 3D Acceleration in general.
+    By the end of this page, the reader will be able to easily enable 3D Acceleration for 
+    their boxes.</p>
+  </comment>
+
+  <p>Boxes now gives you the ability to to enable or disable 3D acceleration for your VMs 
+  if both guest and host support it. This should allow you to improve the performance of 
+  your everyday graphic-hungry applications and games. It uses <sys>Virgil</sys> to create
+  a virtual 3D capable graphics card for your QEMU virtual machines.</p>
+
+  <steps>
+    <title>To enable 3D Acceleration in a box:</title>
+    <item><p>Right-click on the box in the collection view and select
+    <gui>Properties</gui>, or click the menu
+    (<media type="image" src="figures/open-menu-symbolic.svg"><span>settings</span></media>)
+    button in the header bar and select <gui>Properties</gui>.</p></item>
+    <item><p>The <link xref="interface#properties">Properties view</link>
+    opens, with the General tab selected by default.</p></item>
+    <item><p>If 3D Acceleration is supported, the <gui>3D Acceleration</gui> switch would 
+    appear here. By default, it is disabled. To enable 3D Acceleration, simply toggle the 
+    switch next to it to <gui style="switch">ON</gui>.</p></item>
+  </steps>
+
+</page>

help/C/interface.page

@@ -19,6 +19,11 @@
       <email>felipeborges@gnome.org</email>
       <years>2018</years>
     </credit>
+    <credit type="editor">
+      <name>Pranali Deshmukh</name>
+      <email>pranali21293@gmail.com</email>
+      <years>2020</years>
+    </credit>
 
     <include href="legal.xml" xmlns="http://www.w3.org/2001/XInclude"/>
 
@@ -87,9 +92,8 @@
     <item><p><gui>General</gui>: displays the box <gui>Name</gui> and
     <gui>Broker</gui> or virtualizer being used (such as <em>QEMU</em>). For a
     remote box, this tab also displays the <gui>Protocol</gui> (such as
-    <em>VNC</em>), and the <gui>URL</gui> to be used for remote access. When
-    the box is running, the <gui>Share Clipboard</gui> switch appears
-    here.</p></item>
+    <em>VNC</em>), and the <gui>URL</gui> to be used for remote access. The 
+    <gui>3D Acceleration</gui> switch also appears here.</p></item>
     <item><p><gui>System</gui> settings: shows running graphs of CPU, disk I/O
     and network activity. <gui>Memory</gui> and <gui>Maximum Disk Size</gui>
     sliders can be adjusted, and the <gui>Troubleshooting Log</gui> can be

help/meson.build

 help_files = [
+  '3d-acceleration',
   'backup.page',
   'clipboard.page',
   'create.page',