Update method toggle's interface

1. Display the method toggle button by default instead of displaying on hover
2. Only toggle the source code when clicking the method toggle button, not
   when clicking the entire method title section. This will allow us to display
   an anchor link next to the method title
3. Simplify the toggle source button's appearance

Author: st0012

lib/rdoc/generator/template/darkfish/class.rhtml

@@ -109,7 +109,7 @@
                     gsub(/(.*)[-=]>/, '\1→') %>
             </span>
             <%- if i == 0 and method.token_stream then -%>
-            <span class="method-click-advice">click to toggle source</span>
+            <span class="method-click-advice">Toggle source</span>
             <%- end -%>
           </div>
           <%-   end -%>
@@ -122,7 +122,7 @@
             <span class="method-name"><%= h method.name %></span><span
               class="method-args"><%= h method.param_seq %></span>
             <%- if method.token_stream then -%>
-            <span class="method-click-advice">click to toggle source</span>
+            <span class="method-click-advice">Toggle source</span>
             <%- end -%>
           </div>
           <%- end -%>

lib/rdoc/generator/template/darkfish/css/rdoc.css

@@ -608,7 +608,6 @@ main .method-description .method-calls-super {
 
 main .method-detail {
   margin-bottom: 2.5em;
-  cursor: pointer;
 }
 
 main .method-detail:target {
@@ -630,16 +629,12 @@ main .method-heading :visited {
 main .method-click-advice {
   position: absolute;
   top: 2px;
-  right: 5px;
+  right: 0px;
   font-size: 12px;
-  color: #9b9877;
-  visibility: hidden;
   padding-right: 20px;
   line-height: 20px;
-  background: url(../images/zoom.png) no-repeat right top;
-}
-main .method-header:hover .method-click-advice {
-  visibility: visible;
+  color: var(--secondary-color);
+  cursor: pointer;
 }
 
 main .method-alias .method-heading {

lib/rdoc/generator/template/darkfish/js/darkfish.js

@@ -34,7 +34,7 @@ function showSource( e ) {
 };
 
 function hookSourceViews() {
-  document.querySelectorAll('.method-heading').forEach(function (codeObject) {
+  document.querySelectorAll('.method-click-advice').forEach(function (codeObject) {
     codeObject.addEventListener('click', showSource);
   });
 };