breaking changes: 移除最新評論的評論服務商選擇，默認為第一個評論服務商

feat: 增加 waline avatarCDN 配置（最新評論也會更新）
feat: archives 的 標題 在 menu 配置中獲取
fix: 修復文章頁 mathjax 因字體小導致顯示重疊的 bug close #587
fix: 修復 mathjax 在列表下，導致 列表沒有樣式的 bug  close #586
improvement: 減少卡頓，apple 裝置首頁背景 background-attachment 設為 scroll

layout/includes/third-party/newest-comments/index.pug

@@ -1,12 +1,26 @@
-- let config = theme.newest_comments
+- let { use } = theme.comments
 
-if config.valine
-  include ./valine.pug
-else if config.waline
-  include ./waline.pug
-else if config.github_issues.enable
-  include ./github-issues.pug
-else if config.disqus.enable
-  include ./disqus-comment.pug
-else if config.twikoo
-  include ./twikoo-comment.pug
+if use
+  - let forum,apiKey,userRepo
+  case use[0]
+    when 'Valine'
+      include ./valine.pug
+    when 'Waline'
+      include ./waline.pug
+    when 'Twikoo'
+      include ./twikoo-comment.pug
+    when 'Disqus'
+      - forum = theme.disqus.shortname
+      - apiKey = theme.disqus.apikey
+      include ./disqus-comment.pug
+    when 'Disqusjs'
+      - forum = theme.disqusjs.shortname
+      - apiKey = theme.disqusjs.apikey
+      include ./disqus-comment.pug
+    when 'Gitalk'
+      - let { repo,owner } = theme.gitalk
+      - userRepo = owner + '/' + repo
+      include ./github-issues.pug
+    when 'Utterances'
+      - userRepo = theme.utterances.repo
+      include ./github-issues.pug