chore(*): update default thumbnail image and a style fix

includes/helpers/page.js

@@ -91,6 +91,6 @@ module.exports = function (hexo) {
 
     hexo.extend.helper.register('get_thumbnail', function (post) {
         const hasThumbnail = hexo.extend.helper.get('has_thumbnail').bind(this)(post);
-        return this.url_for(hasThumbnail ? post.thumbnail : 'images/thumbnail.png');
+        return this.url_for(hasThumbnail ? post.thumbnail : 'images/thumbnail.svg');
     });
 }

source/css/style.styl

@@ -249,6 +249,10 @@ img.thumbnail
     code, pre
         font-size: 0.8em
         font-family: family-mono
+    blockquote
+        footer
+            strong + cite
+                margin-left: 0.5em
 
 /* ---------------------------------
  *        Fix code highlight

source/images/thumbnail.svg

@@ -0,0 +1,9 @@
+<svg
+    xmlns="http://www.w3.org/2000/svg" viewBox="0 0 50 50" fill="#ccc">
+    <rect width="100%" height="100%" fill="#f2f2f2"/>
+    <path d="M39 38H11c-1.7 0-3-1.3-3-3V17c0-1.7 1.3-3 3-3h6c.2 0 .5-.2.6-.3l1.1-2.2c.4-.8 1.4-1.4 2.3-1.4h8c.9 0 1.9.6 2.3 1.4l1.1 2.2c.1.2.4.3.6.3h6c1.7 0 3 1.3 3 3v18c0 1.7-1.3 3-3 3zM11 16c-.6 0-1 .4-1 1v18c0 .6.4 1 1 1h28c.6 0 1-.4 1-1V17c0-.6-.4-1-1-1h-6c-.9 0-1.9-.6-2.3-1.4l-1.1-2.2c-.1-.2-.4-.4-.6-.4h-8c-.2 0-.5.2-.6.3l-1.1 2.2c-.4.9-1.4 1.5-2.3 1.5h-6z"/>
+    <path d="M25 34c-5 0-9-4-9-9s4-9 9-9 9 4 9 9-4 9-9 9zm0-16c-3.9 0-7 3.1-7 7s3.1 7 7 7 7-3.1 7-7-3.1-7-7-7z"/>
+    <circle cx="35" cy="18" r="1"/>
+    <path d="M12 12h4v1h-4z"/>
+    <path d="M25 21v-1c-2.8 0-5 2.2-5 5h1c0-2.2 1.8-4 4-4z"/>
+</svg>