docs: Add stub articles for search guides

[m-allanson]

Description

Update the existing search guide to act as an overview for more specific guides.

I've also updated the [[guidelist]] handler to remove the hardcoded paths (cc @jlengstorf)

Related Issues

Refs #10113

[jonniebigodes]

@m-allanson i'm working on documentating how to search with reactivesearch. I can expand the document i'm producing for both of elasticunr and js-search also. Algolia for me it's not something i really not that confortable, so i'll refrain from expanding that stub and probably fumble fingering it.

[DSchau]

This looks great! Left a comment on a code style thing, feel free to take or leave it!

[DSchau]

This looks better, but I wonder if we could make it less side-effecty with a .find and perhaps a flatten? Here's a start:

const flatten = arr => arr.reduce((merged, item) => merged.concat(Array.isArray(item.items) ? flatten(item.items) : item), [])

const findBySlug = (guides, slug) => {
  return flatten(guides)
    .find(item => item.link === slug)
}

[DSchau]

Presuming we have a structure like (for guides):

const guides = [
    {
      link: '/test'
    },
    {
      items: [
        {
          link: '/test2'
        }
      ]
    }
  ]

this seems to work just fine!

[m-allanson]

I had a little play around with this but I don't think flatten is right here, as we want to grab the child items from the item with the matching slug. I rejigged some other bits while playing around with this though, thank you 👍

[jonniebigodes]

ok, so with this merge now my pull request #11030 is basically throwing merge conflicts with what is now the master. If you don't mind, a little feedback would be appreciated on this matter

[m-allanson]

Sorry I missed your comment earlier, I've fixed up the merge conflicts on your branch.