how do i create an index with settings

### Type of issue

None

### What documentation page is affected

https://www.elastic.co/docs/manage-data/data-store/index-basics

### What happened?

We should have a basic API call on creating an index with settings on this page

### action
assess the page for opportunities to add API examples, add them where possible. we have inconsistent usage of API examples, e.g. the index templates process on the page creates an index with a template, but there's no basic index example.

you might be able to use other instances from other areas of our docs