feat: Add "Close Guide" button to <page-guide>

Upon clicking, this button emits a `guide-close` event with no args.

Author: pastelmind

css/page-guide.css

@@ -10,6 +10,25 @@
   box-shadow: 1px 1px 10px black;
 }
 
+.page-guide__header {
+  display: flex;
+}
+
+.page-guide__close-button {
+  align-self: flex-start;
+  background: none;
+  border: 1px solid transparent;
+  border-radius: 0.5rem;
+  cursor: pointer;
+  font-size: 1.5rem;
+  margin-left: auto; /* Push the button to the right end */
+}
+
+.page-guide__close-button:hover {
+  background-color: #fff;
+  border-color: black;
+}
+
 .page-guide__author {
   font-style: italic;
   font-weight: bold;

index.html

@@ -26,7 +26,16 @@ <h1 class="logo">RiftGuide</h1>
 
     <template id="template-page-guide">
       <div class="page-guide">
-        <h2 class="page-guide__title">{{guide.title}}</h2>
+        <header class="page-guide__header">
+          <h2 class="page-guide__title">{{guide.title}}</h2>
+          <button
+            class="page-guide__close-button"
+            title="Close guide"
+            @click="$emit('guide-close')"
+          >
+            <i class="fas fa-arrow-circle-left"></i>
+          </button>
+        </header>
         <address class="page-guide__author">Author: {{guide.author}}</address>
         <div class="page-guide__body">
           <section