update indexes.md

[maryamsulemani97]

Part of #1333

This PR updates /learn/core_concepts/indexes.md
I have added the remaining index settings to this page and now it's similar to Index settings

[dichotommy]

Some thoughts in no particular order:

The way we use links and bold on the documentation have really changed from the time this guide was written / last updated. These days, I try not to link multiple times in the same sentence if I can avoid it. I also try to explain where the link will take the user in the hyperlinked text; as a result I avoid one-word links more and more.

I'm unable to comment on line 37, but I would like to rewrite the "primary key" section of this page from the perspective of an index. Something like this: "Every index has a primary key: a required attribute that must be present in all documents in the index. Each document in the index must have a unique value associated with the primary key. This serves to identify each document in the index, such that two documents in an index can never be completely identical." Actually, if you don't want to use this, the description in the linked section of the primary key guide is pretty good.

When it comes to the settings descriptions, I'm basically taking what you did for Synonyms and using it as a template for the others. This is something I would encourage you to do as well in the future. If you know you're going to be describing a lot of similar things, it's always best to try to stick to a consistent format that contains only the essential information (in this case, a brief description, links to API reference pages, and link to dedicated guide).

Once this PR is merged, I think we will be in a good position to tackle eliminating the Settings "overview" guide.

[dichotommy]

Almost there! ⛰️ 🚴🏻

Comments have been addressed

[guimachiavelli]

🦞

[maryamsulemani97]

bors merge

[bors]

Build succeeded:

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