Enable lazy_image_tag in Podcasts resources

Author: yasulab

app/views/podcasts/index.html.erb

@@ -3,13 +3,13 @@
 <% provide(:url,   @url ) %>
 <% provide(:meta_image,  "/img/ogp-dojocast.jpeg") %>
 
-<img class="dojocast-cover lazyload" alt="DojoCast Cover Photo" src="/spinner.svg" data-src="/img/dojocast-cover.jpg" loading='lazy' />
+<%= lazy_image_tag('/podcasts/dojocast-cover.jpg', alt: 'DojoCast Cover Photo', class: 'dojocast-cover') %>
 
 <div class="container" style="line-height: 2.2em;">
   <section class="doc" style="padding: 50px 0px 0px 0px;">
     <h1 style="text-align: center;"><%= @title %></h1>
     <p style="text-align: center; padding-bottom: 10px;">CoderDojo コミュニティに関わる人々を<br class="ignore-pc">ハイライトするポッドキャスト番組です 📻✨</p>
-    <img class="lazyload" src="/podcasts/cover-sub.jpg" alt="インタビューの様子"/>
+    <%= lazy_image_tag('/podcasts/cover-sub.jpg', alt: 'DojoCast の収録の様子') %>
 
     <div class='text-center' style="margin-top: 30px;">
       <div class="g-ytsubscribe" data-channelid="UCal5GuoCDCMDQe07w69TuJA" data-layout="full" data-count="default"></div>

app/views/podcasts/show.html.erb

@@ -3,7 +3,7 @@
 <% provide(:url,   @url) %>
 <% provide(:meta_image,  @episode.cover) %>
 
-<img class="dojocast-cover" alt="DojoCast Cover Photo" src="/img/dojocast-cover.jpg" />
+<%= lazy_image_tag('/podcasts/dojocast-cover.jpg', alt: 'DojoCast Cover Photo', class: 'dojocast-cover') %>
 
 <style type="text/css">
   .prev { display: table-cell; font-color: white; text-align: left;   }