breaking changes: cover 的顯示優化 #1101

feature: default_cover 可配置顏色
fix: 修復使用本地搜索時，輸入特殊符號沒有顯示結果的 bug closed #1110
fix: 修復 頂部圖和 footer 配置帶有/的顏色參數時，無法顯示顏色的 bug
improvement: 鼠標移動到分頁時，文章分頁按鈕增加説明文字
improvement: 文章頁的頂部圖顯示次序為 top_img > cover > default_top_img
improvement: canonical 的鏈接根據配置生成 #1111

scripts/helpers/related_post.js

@@ -15,7 +15,7 @@ hexo.extend.helper.register('related_posts', function (currentPost, allPosts) {
           title: post.title,
           path: post.path,
           cover: post.cover,
-          randomcover: post.randomcover,
+          cover_type: post.cover_type,
           weight: 1,
           updated: post.updated,
           created: post.date
@@ -50,13 +50,14 @@ hexo.extend.helper.register('related_posts', function (currentPost, allPosts) {
     result += '<div class="relatedPosts-list">'
 
     for (let i = 0; i < Math.min(relatedPosts.length, limitNum); i++) {
-      const cover =
-        relatedPosts[i].cover === false
-          ? relatedPosts[i].randomcover
-          : relatedPosts[i].cover
+      const cover = relatedPosts[i].cover || 'var(--default-bg-color)'
       const title = this.escape_html(relatedPosts[i].title)
       result += `<div><a href="${this.url_for(relatedPosts[i].path)}" title="${title}">`
-      result += `<img class="cover" src="${this.url_for(cover)}" alt="cover">`
+      if (relatedPosts[i].cover_type === 'img') {
+        result += `<img class="cover" src="${this.url_for(cover)}" alt="cover">`
+      } else {
+        result += `<div class="cover" style="background: ${cover}"></div>`
+      }
       if (dateType === 'created') {
         result += `<div class="content is-center"><div class="date"><i class="far fa-calendar-alt fa-fw"></i> ${this.date(relatedPosts[i].created, hexoConfig.date_format)}</div>`
       } else {