Upgrade Docusaurus to 3.9.2

[wuchong]

Search before asking

• I searched in the issues and found nothing similar.

Description

Docusaurus 3.9.2 was released last month (https://docusaurus.io/changelog/3.9.2), and we can upgrade it by running following npm i command.

➜  website git:(main) npm run start

> fluss-website@0.0.0 start
> docusaurus start


    --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- 
                                                                                                                                                                                                        
                                                                                      Update available 3.8.1 → 3.9.2                                                                                    
                                                                                                                                                                                                        
                                                             To upgrade Docusaurus packages with the latest version, run the following command:                                                         
         `npm i @docusaurus/core@latest @docusaurus/plugin-pwa@latest @docusaurus/preset-classic@latest @docusaurus/module-type-aliases@latest @docusaurus/tsconfig@latest @docusaurus/types@latest`    
                                                                                                                                                                                                        
    --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- 

Willingness to contribute

• I'm willing to submit a PR!

[rionmonster]

@wuchong

I can take this -- it should be pretty trivial. I also noticed testing it appeared to yield the following warning about a future deprecation. Should we take care of that as part of this upgrade (seems to be a minor configuration change):

[WARNING] The `siteConfig.onBrokenMarkdownLinks` config option is deprecated and will be removed in Docusaurus v4.
Please migrate and move this option to `siteConfig.markdown.hooks.onBrokenMarkdownLinks` instead.

[rionmonster]

I've gone ahead and put together the pull request for this.

The deprecation fix was extremely minor so I included it as part of this effort (since it's directly related to the Docusaurus upgrade). The changes also required upgrading to Node v20 (per Docusaurus dropping support for Node v18) which I've done as well.