Documentation: Recipe tutorial does not explain how to use the index

[rptb1]

Describe the bug
The recipe tutorial shows how to create an index of recipes, but it never explains how to get that index to appear in the output.

To Reproduce

1. Follow the recipe tutorial.
2. Try to get the index to appear when you don't know how.

Expected behavior
There should be a paragraph explaining where the index is generated in the build, and how to include it in the output document, with a code sample.

Note: This may look like a request for support, but I'd like the documentation improved for all. Thanks!

[tk0miya]

+1: But I'm not familiar with index page...

[mzjn]

It looks like this was fixed by #11049.