add initial section on accessibility

static/usage.html

@@ -55,6 +55,7 @@
             <nav id="table-of-contents">
                 <h2><a href="#table-of-contents">Table of contents</a></h2>
                 <ul>
+                    <li><a href="#accessibility">Accessibility</a></li>
                     <li><a href="#auditor">Auditor</a></li>
                     <li>
                         <a href="#updates">Updates</a>
@@ -80,6 +81,41 @@
                 </ul>
             </nav>
 
+            <section id="accessibility">
+                <h2><a href="#accessibility">Accessibility</a></h2>
+
+                <p>GrapheneOS includes all of the accessibility features from the Android Open
+                Source Project and strives to fill in the gaps from not including Google apps and
+                services. We include our own fork of the open source TalkBack and Switch Access
+                accessibility services along with a Monochromacy option for the standard color
+                correction menu.</p>
+
+                <p>GrapheneOS does not yet include a text-to-speech (TTS) service in the base OS
+                due to limitations of the available options. Including one is planned in the
+                future when a suitable option is available. RHVoice and eSpeak NG are both open
+                source and are the most common choices by GrapheneOS users. Both of these mostly
+                work fine but have licensing issues and don't support Direct Boot so they cannot
+                be used before the initial unlock of the device. Installing and setting up either
+                one of these or another TTS app will get TalkBack working. TalkBack itself
+                supports Direct Boot and works before the first unlock but it needs to have a TTS
+                app supporting it in order to do more than playing the activation sound before the
+                first unlock. After installing a TTS service, you need to select it in the OS
+                configuration to accept activating it. The OS will display one of them as already
+                selected but it won't simply work from being installed as that wouldn't be safe.
+                This is the same as the stock OS but it comes with one set up already.</p>
+
+                <p>GrapheneOS disables showing the characters as passwords are typed by default.
+                You can enable this in Settings ➔ Privacy.</p>
+
+                <p>Third party accessibility services can be installed and activated. This
+                includes the ones made by Google. Most of these will work but some may have a hard
+                dependency on functionality from Google Play services for some of their
+                functionality or to run at all. Accessibility services are very powerful and we
+                strongly recommend against using third party implementations if you can get by
+                well without them. We plan to add safeguards in this area while still keeping them
+                working without problematic barriers.</p>
+            </section>
+
             <section id="auditor">
                 <h2><a href="#auditor">Auditor</a></h2>
                 <p>See the <a href="https://attestation.app/tutorial">tutorial page on the site for the attestation sub-project</a>.</p>