feat: add mermaid support (#75)

usage

1. enable mermaid in post's front matter, e.g.

   ---
   mermaid: true

2. include content with `<div>`, e.g.

   <div class="mermaid">
   graph TD;
       A-->B;
       A-->C;
       B-->D;
       C-->D;
   </div>

2 files changed, 18 insertions, 0 deletions

diff --git a/config-examples/en/config.toml b/config-examples/en/config.toml
index 79d056d..4676c74 100644
--- a/config-examples/en/config.toml
+++ b/config-examples/en/config.toml
@@ -606,6 +606,15 @@ uglyURLs = false
 
 
     ######################################
+    # Mermaid (https://github.com/mermaid-js/mermaid)
+
+    enableMermaid = false
+    # Note: *global settings*
+    #       `mermaid` in post’s Front Matter
+    #       has a higher priority than here
+
+
+    ######################################
     # Comments
 
     # Note: render only in production
diff --git a/config-examples/zh-cn/config.toml b/config-examples/zh-cn/config.toml
index 216312f..6001835 100644
--- a/config-examples/zh-cn/config.toml
+++ b/config-examples/zh-cn/config.toml
@@ -557,6 +557,15 @@ uglyURLs = false
 
 
     ######################################
+    # Mermaid (https://github.com/mermaid-js/mermaid)
+
+    # 是否开启（全局设置）
+    enableMermaid = false
+    # 说明：文章的 Front Matter 中的 `mermaid`
+    #      的优先级高于此处
+
+
+    ######################################
     # 评论
 
     # 说明：仅在生产环境（production）下渲染