Add mermaid support (#857)

Closes #825


Co-authored-by: Matt Wang <matt@matthewwang.me>

_config.yml

@@ -51,6 +51,27 @@ search:
   # Supports true or false (default)
   button: false
 
+# Enable or disable support for mermaid diagrams (https://mermaid-js.github.io/mermaid/)
+# Supports true or false (default)
+mermaid_enabled: false
+mermaid:
+  # Version of mermaid library
+  # Pick an available version from https://cdn.jsdelivr.net/npm/mermaid/
+  version: "9.1.3"
+  # Configured theme of mermaid diagrams
+  # Pick an avaiable theme from https://mermaid-js.github.io/mermaid/#/theming
+  theme: "default"
+  # Additional configuration available matching pattern as defined in https://mermaid-js.github.io/mermaid/#/./Setup.
+  # For example,
+  # logLevel: 'fatal',
+  # sequence:
+  #   diagramMarginX: 50
+  #   actorMargin: 50
+  # gantt:
+  #   barGap: 4
+  #   topPadding: 50
+
+
 # Enable or disable heading anchors
 heading_anchors: true