feat: Conditionally load Mermaid.js

[donglua]

This change modifies the post layout to only include the Mermaid.js script if the post content contains a Mermaid diagram. This is achieved by checking for the presence of the "language-mermaid" string in the post's content. This change improves page load performance by avoiding the unnecessary loading of the Mermaid.js library on pages that do not contain any diagrams.

[gemini-code-assist]

Summary of Changes

Hello @donglua, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request implements a performance optimization by introducing conditional loading for the Mermaid.js library. Instead of including the script on every post page, it will now only be loaded when a post is detected to contain a Mermaid diagram. This targeted approach ensures that resources are only consumed when necessary, leading to faster page rendering for content without diagrams.

Highlights

• Conditional Script Loading: The Mermaid.js script is now conditionally loaded in _layouts/post.html. It will only be included if the post's content contains the string 'language-mermaid', indicating the presence of a Mermaid diagram.
• Performance Improvement: This change optimizes page load performance by preventing the unnecessary loading of the Mermaid.js library on pages that do not contain any diagrams, reducing bandwidth and processing overhead.

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[gemini-code-assist]

Code Review

This pull request introduces a good performance optimization by loading Mermaid.js conditionally, only when a diagram is present in the post content. The approach of checking for the 'language-mermaid' string is a sensible and pragmatic way to achieve this. My review includes one suggestion to improve code formatting for better readability and consistency.

[gemini-code-assist]

For better readability and to maintain a consistent coding style with the rest of the file, please consider indenting the include tag within the if block.

  {% include mermaid.html %}