added go back anchor on error pages

public/404.html

@@ -46,6 +46,14 @@
       margin: 40px auto;
     }
 
+    a {
+      line-height: 100px;
+      font-weight: normal;
+      color: #4A8BEE;
+      font-size: 18px;
+      text-decoration: none;
+    }
+
     .container {
       margin: auto 20px;
     }
@@ -63,6 +71,7 @@
     <hr />
     <p>Make sure the address is correct and that the page hasn't moved.</p>
     <p>Please contact your GitLab administrator if you think this is a mistake.</p>
+    <a href="javascript:history.back()">Go back</a>
   </div>
 </body>
 </html>

public/422.html

@@ -46,6 +46,14 @@
       margin: 40px auto;
     }
 
+    a {
+      line-height: 100px;
+      font-weight: normal;
+      color: #4A8BEE;
+      font-size: 18px;
+      text-decoration: none;
+    }
+
     .container {
       margin: auto 20px;
     }
@@ -63,6 +71,7 @@
     <hr />
     <p>Make sure you have access to the thing you tried to change.</p>
     <p>Please contact your GitLab administrator if you think this is a mistake.</p>
+    <a href="javascript:history.back()">Go back</a>
   </div>
 </body>
 </html>

public/500.html

@@ -46,6 +46,14 @@
       margin: 40px auto;
     }
 
+    a {
+      line-height: 100px;
+      font-weight: normal;
+      color: #4A8BEE;
+      font-size: 18px;
+      text-decoration: none;
+    }
+
     .container {
       margin: auto 20px;
     }
@@ -63,6 +71,7 @@
     <hr />
     <p>Try refreshing the page, or going back and attempting the action again.</p>
     <p>Please contact your GitLab administrator if this problem persists.</p>
+    <a href="javascript:history.back()">Go back</a>
   </div>
 </body>
 </html>

public/502.html

@@ -46,6 +46,14 @@
       margin: 40px auto;
     }
 
+    a {
+      line-height: 100px;
+      font-weight: normal;
+      color: #4A8BEE;
+      font-size: 18px;
+      text-decoration: none;
+    }
+
     .container {
       margin: auto 20px;
     }
@@ -63,6 +71,7 @@
     <hr />
     <p>Try refreshing the page, or going back and attempting the action again.</p>
     <p>Please contact your GitLab administrator if this problem persists.</p>
+    <a href="javascript:history.back()">Go back</a>
   </div>
 </body>
 </html>

public/503.html

@@ -46,6 +46,14 @@
       margin: 40px auto;
     }
 
+    a {
+      line-height: 100px;
+      font-weight: normal;
+      color: #4A8BEE;
+      font-size: 18px;
+      text-decoration: none;
+    }
+
     .container {
       margin: auto 20px;
     }
@@ -63,6 +71,7 @@
     <hr />
     <p>Try refreshing the page, or going back and attempting the action again.</p>
     <p>Please contact your GitLab administrator if this problem persists.</p>
+    <a href="javascript:history.back()">Go back</a>
   </div>
 </body>
 </html>