User guides: add a 'Back to the list' at the bottom of every guide

_i18n/en.yml

@@ -512,6 +512,7 @@ user-guides:
   node-i2pzero: Run a Monero node through I2P with I2P-zero
   guiguide: Guide for the Monero GUI wallet
   tailsguide: Set up a wallet (using a remote node) on Tails
+  back: Back to the list
 
 roadmap:
   completed: Completed task

_layouts/user-guide.html

@@ -7,6 +7,9 @@ layout: base
                 <div class="info-block text-adapt">
                     <div>
                         {{content}}
+                        <p style="text-align: right;">
+                            <a href="{{ site.baseurl }}/resources/user-guides/">&laquo; {% t user-guides.back %}</a>
+                        </p>
                     </div>
                 </div>
         </section>