Dynamic sitemap generation

[TG199]

### Type of Change

• [ ] New feature (non-breaking change which adds functionality)

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Hi @benedikt-bartscher, I hope you're well. Apologies for the delay in updating you on this issue. Here is a proposed solution for generating dynamic sitemaps in Reflex apps.

Changes Made

1. Added a Placeholder Constant:

   • Introduced a new placeholder constant in the Next constant variables.

2. Updated next_sitemap.js:

   • Assigned the placeholder constant to siteUrl in the `gener

3. Implemented Dynamic Sitemap Generation:

   • Developed a method to generate dynamic sitemaps based on the application's routes.

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Feel free to let me know if there are any questions or further adjustments needed.

[Alek99]

Nice idea! Do you have a link to issue

[benedikt-bartscher]

Thanks, @TG199 I'll try this out and review it later this week.

@Alek99 it's issue #3489