fix(a11y): Add missing required "alt" attribute

Signed-off-by: txtsd <code@ihavea.quest>

main.html

@@ -24,9 +24,9 @@
 <div class="vbox window" id="main">
 
 <div id="titlebar">
-  <img src="swords.gif">
+  <img src="swords.gif" alt="Progress Quest Logo">
   <span id="title">Progress Quest</span>
-  <a id="quit"><img src="closeup.png"></a>
+  <a id="quit"><img src="closeup.png" alt="Close button"></a>
 </div>
 
 <script src="json2.js"></script>

newguy.html

@@ -24,9 +24,9 @@ input, button { display: inline; }
 <div class="vbox window" id="newguy">
 
   <div id="titlebar">
-    <img src="swords.gif">
+    <img src="swords.gif" alt="Progress Quest Logo">
     <span>Progress Quest - New Character</span>
-    <a id="quit"><img src="closeup.png"></a>
+    <a id="quit"><img src="closeup.png" alt="Close button"></a>
   </div>
 
   <div class="client">

roster.html

@@ -101,7 +101,7 @@ img {
   <tr>
     <td id="newc">
       <b>New Character</b><br>
-      <img src="dicebar.jpg"><br>
+      <img src="dicebar.jpg" alt="four dice"><br>
       <button id="roll">Roll One Up</button>
     </td>
   </tr>