Improve some image descriptions.

api/index.html

@@ -14,7 +14,7 @@ <h1>SeriesGuide Extensions API</h1>
 
     <p>The button might link to external content (app deep-link, web page, ...) or trigger an action in another app (play, record, ...). Or it can just display some status information (such as "downloaded").</p>
 
-    <img src="/images/extensions-780x280.png" width="360" alt="Extensions examples" />
+    <img src="/images/extensions-780x280.png" width="360" alt="Screenshot showing example extensions and the customize extensions button." />
 
     <h3 class="mt-3">Add or remove an extension</h3>
     <p>When viewing an episode or movie, scroll to the bottom and tap <strong>Customize extensions</strong>.</p>

help.html

@@ -201,7 +201,7 @@ <h3>Images are not displayed</h3>
         <dt>Image cache is corrupted</dt>
         <dd>You can try clearing the cache for SeriesGuide. Tap <strong>More</strong> <span class="material-symbols-outlined" aria-hidden="true">menu</span> > <b>Settings</b> > <b>Clear image cache</b>. In the App Info screen that opens, go to Storage and tap Clear Cache.</dd>
 
-        <img src="images/cache-settings-780x238.png" width="390" alt="Clear Cache Settings screen" />
+        <img src="images/cache-settings-780x238.png" width="390" alt="Screenshot of Clear Cache button on settings screen." />
 
         <dt class="mt-3"><em>Images over Wi-Fi only</em> is enabled</dt>
         <dd>If your current connection is metered and this setting is enabled, no images are downloaded. Tap <strong>More</strong> <span class="material-symbols-outlined" aria-hidden="true">menu</span> > <b>Settings</b> and disable the setting.</dd>
@@ -272,7 +272,7 @@ <h3>Hide the SeriesGuide X app icon from the launcher</h3>
     <section class="mt-2">
       <h3>Check in, set watched, add to collection and skip</h3>
       <p>Each episode or movie displays a button bar with up to four actions:</p>
-      <p><img src="images/buttons-780x238.png" alt="Episode actions" width="390" class="img-responsive"></p>
+      <p><img src="images/buttons-780x238.png" alt="Screenshot showing episode action buttons." width="390" class="img-responsive"></p>
       <ul>
           <li><a href="#checkins">Check in via Trakt</a> if you are watching right now. (<strong>Not available</strong> if SeriesGuide Cloud is connected.)</li>
           <li><b>Set watched</b> if you have watched this.</li>

index.html

@@ -23,7 +23,7 @@ <h2 id="app-description">SeriesGuide helps you keep track of your favorite TV sh
   </div>
 
   <div class="col-sm-6 col-md-7">
-    <img src="images/hero.png" class="img-fluid d-block mx-auto mt-sm-3 img-hero" alt="show list screenshot"/>
+    <img src="images/hero.png" class="img-fluid d-block mx-auto mt-sm-3 img-hero" alt="Screenshot showing the main screen of SeriesGuide with a list of shows."/>
   </div>
 </div>