set article view width limit

src/assets/index.html

@@ -334,6 +334,7 @@
                  class="content px-4 pt-3 pb-5 border-top overflow-auto"
                  :class="{'font-serif': theme.font == 'serif', 'font-monospace': theme.font == 'monospace'}"
                  :style="{'font-size': theme.size + 'rem'}">
+                <div class="content-wrapper">
                     <h1><b>{{ itemSelectedDetails.title || 'untitled' }}</b></h1>
                     <div class="text-muted">
                         <div>{{ feedsById[itemSelectedDetails.feed_id].title }}</div>
@@ -347,6 +348,7 @@
                     <div v-html="itemSelectedContent"></div>
                 </div>
             </div>
+        </div>
         <modal :open="!!settings" @hide="settings = ''">
             <button class="btn btn-link outline-none float-right p-2 mr-n2 mt-n2" style="line-height: 1" @click="settings = ''">
                 <span class="icon">{% inline "x.svg" %}</span>

src/assets/stylesheets/app.css

@@ -353,6 +353,11 @@ select.form-control:not([multiple]):not([size]) {
   line-height: 1.5;
 }
 
+.content-wrapper {
+  max-width: 60rem;
+  margin: 0 auto;
+}
+
 .content img, .content video {
   max-width: 100%;
   height: auto;