Render permalink as link icon

The `link.svg` file is from [Feather icons][feather] v4.29.0, and is
[licensed under the MIT license][license].

[feather]: https://feathericons.com/
[license]: https://github.com/feathericons/feather/blob/v4.29.0/LICENSE

Author: jonathanhefner

lib/rdoc/generator/template/rails/_context.rhtml

@@ -131,8 +131,11 @@
       <h2 class="content__divider"><%= visibility.to_s.capitalize %> <%= type %> methods</h2>
       <% methods.each do |method| %>
         <div class="method" id="<%= method.aref %>">
-          <h3 class="method__signature"><%= method_signature method %></h3>
-          <%= link_to "Link", method, class: "permalink", name: method.aref %>
+          <div class="method__signature">
+            <h3><%= method_signature method %></h3>
+            <%= link_to %(<img src="/i/link.svg" alt="Permalink">), method,
+                  class: "method__permalink", title: "Permalink" %>
+          </div>
 
           <% unless method.aliases.empty? %>
             <p class="method__aka">

lib/rdoc/generator/template/rails/resources/css/main.css

@@ -160,9 +160,6 @@ dt
   overflow-x: auto;
 }
 
-.method {
-    position: relative;
-}
 .method h4
 {
     border-bottom: 1px dotted #999;
@@ -172,13 +169,6 @@ dt
     color: var(--heading-color);
 }
 
-.method a.permalink {
-  position: absolute;
-  font-size: 0.9em;
-  right: 0;
-  top: 0;
-}
-
 @keyframes spotlight {
   from { background-color: yellow; }
   to { background-color: white; }
@@ -485,10 +475,27 @@ html {
 
 .method__signature {
   font-size: 1.1em;
-  font-weight: normal;
-  white-space: pre-wrap;
   padding-bottom: var(--space-sm);
   border-bottom: 2px solid var(--code-bg);
+
+  display: flex;
+  align-items: baseline;
+}
+
+.method__signature h3 {
+  font-size: 1em;
+  font-weight: normal;
+  white-space: pre-wrap;
+}
+
+.method__permalink {
+  margin: 0 0 0 0.5em;
+}
+
+.method__permalink img {
+  font-family: monospace; /* Make em equivalent to <code>'s em */
+  height: 1em;
+  vertical-align: middle;
 }
 
 .method__aka {

lib/rdoc/generator/template/rails/resources/css/reset.css

@@ -10,9 +10,7 @@ b, u, i, center,
 dl, dt, dd, ol, ul, li,
 fieldset, form, label, legend,
 table, caption, tbody, tfoot, thead, tr, th, td {
-	border: 0;
 	font-size: 100%;
-	vertical-align: baseline;
 	background: transparent;
 }
 blockquote, q {