Support sitemap Etag Header

[sonofmagic]

What problem does this feature solve?

Sitemap with Rtag can speed up search engine crawling. Baidu search engine can respond to sitemap updates more quickly. refer:https://ziyuan.baidu.com/college/articleinfo?id=456

What does the proposed changes look like?

options:{
Etag:true
}

_{This feature request is available on Nuxt community (#c63)}

[NicoPennec]

I was not aware of this optimization by Etag Header optmization for the Baidu search engine 👍

We should be able to take inspiration from this code from Nuxt: https://github.com/nuxt/nuxt.js/blob/76b1167d27b39a19ae2556334cd59e04ae19c1a8/packages/server/src/middleware/nuxt.js#L39-L49

[NicoPennec]

The ETag is now enabled by default, since release v2.2.0.
To override the default config, see docs

Thank @sonofmagic for your proposal 🙏
It's a useful enhance for performance.