fix: Use a main tag for the main part of the page

See https://dequeuniversity.com/rules/axe/2.2/bypass?application=lighthouse

templates/error.tpl

@@ -1,6 +1,6 @@
 {include file='inc/head.tpl'}
 <div class="wrapper">
-    <div class="main error">
+    <main class="main error">
         {include file="inc/logo.tpl"}
         <h2>{t}An error occurred{/t}</h2>
         {t}Please check the URL of your video.{/t}
@@ -10,5 +10,5 @@
             <br/>
         {/foreach}
         </i></p>
-</div>
+    </main>
 {include file='inc/footer.tpl'}

templates/index.tpl

@@ -1,6 +1,6 @@
 {include file='inc/head.tpl'}
 {include file='inc/header.tpl'}
-<div class="main">
+<main class="main">
     <div><img class="logo" src="{base_url}/img/logo.png"
     alt="AllTube Download" width="328" height="284"></div>
     <form action="{path_for name="video"}">
@@ -32,5 +32,5 @@
         <a class="bookmarklet small-font" href="javascript:window.location='{$domain}{path_for name='video'}?url='+encodeURIComponent(location.href);">{t}Bookmarklet{/t}</a>
     </div>
 
-</div>
+</main>
 {include file='inc/footer.tpl'}

templates/password.tpl

@@ -1,6 +1,6 @@
 {include file='inc/head.tpl'}
 <div class="wrapper">
-    <div class="main">
+    <main class="main">
         {include file="inc/logo.tpl"}
         <h2>{t}This video is protected{/t}</h2>
         <p>{t}You need a password in order to download this video.{/t}</p>
@@ -9,5 +9,5 @@
             <br/><br/>
             <input class="downloadBtn" type="submit" value="{t}Download{/t}" />
         </form>
-    </div>
+    </main>
 {include file='inc/footer.tpl'}

templates/playlist.tpl

@@ -1,6 +1,6 @@
 {include file="inc/head.tpl"}
 <div class="wrapper">
-<div class="main">
+<main class="main">
 {include file="inc/logo.tpl"}
 <p>{t}Videos extracted from{/t} {if isset($video->title)}<i>
     <a href="{$video->webpage_url}">
@@ -28,5 +28,5 @@
     </div>
 {/foreach}
 
-</div>
+</main>
 {include file="inc/footer.tpl"}

templates/video.tpl

@@ -1,7 +1,7 @@
 {include file="inc/head.tpl"}
 <div class="wrapper">
 <div itemscope itemtype="http://schema.org/VideoObject">
-<div class="main">
+<main class="main">
 {include file="inc/logo.tpl"}
 <p id="download_intro">{t}You are going to download{/t}<i itemprop="name">
     <a itemprop="url" id="video_link"
@@ -85,6 +85,6 @@
 {else}
     <input class="downloadBtn" type="submit" value="{t}Download{/t}" /><br/>
 {/if}
-</div>
+</main>
 </div>
 {include file="inc/footer.tpl"}