feat: add support for mermaid diagrams (#244)

data/config.yaml

@@ -11,6 +11,7 @@ enableFooter: true
 enableContextualBacklinks: true
 enableRecentNotes: false
 enableGitHubEdit: true
+enableMermaid: true
 GitHubLink: https://github.com/jackyzha0/quartz/tree/hugo/content
 search:
   enableSemanticSearch: false