refactor(tagcloud): switch custom_colors from inline styles to CSS classes

source/css/_page/tags.styl

@@ -89,3 +89,16 @@
 .page-title
   & + .tag-cloud-list
     text-align: left
+
+tag_colors = hexo-config('aside.card_tags.custom_colors')
+
+.tag-cloud-list .tag-cloud-item
+  background-color var(--tag-cloud-color)
+
+.card-tag-cloud .tag-cloud-item
+  color var(--tag-cloud-color)
+
+if tag_colors && length(tag_colors) > 0
+  for c, i in tag_colors
+    .tag-cloud-item.tag-color-{i}
+      --tag-cloud-color convert(c)