HBASE-30127 Improve Website's SEO

[yuriipalam]

There is also a small change in the hbase-site repo, please take a look:
apache/hbase-site#13

This change improves SEO (Search Engine Optimization) by adding proper cache headers, good looking 404 page, and sitemap.

404 page in dark mode:

[PDavid]

Many thanks, looks really nice already. 👍

Just two small questions / comments.

[PDavid]

It seems that the build complains about these files missing the ASF licence header:

Files with unapproved licenses:

public/robots.txt
public/sitemap.xml

[PDavid]

Many thanks, looks good to me. 👍

[PDavid]

Some tests failed in the PR build but they are not because of the changes in this branch.

[PDavid]

Can I ask why did we remove this footnote from here? It seems to be unrelated to the website SEO to me.

[yuriipalam]

Because this footnote was added to the heading, what leads to a nested link problem.
In docs frameworks headings are links because they are anchors, same for footnotes.
So we had something like

<a>
  <h4>Heading...</h4>
  <a>^3</a>
<a>

It's wrong HTML structure which leads to a hydration error. Due to the async nature of the e2e tests, we couldn't reliably catch this issue before. It might be a new task to work on for me actually, to make it more deterministic.

So, I just moved the footnote right under the heading since it's the only place where it's used. This way we fix the broken structure.