make directive basics more prominent (#2972)

Author: shainaraskas

docs/_docset.yml

@@ -110,6 +110,7 @@ toc:
     children:
       - file: index.md
       - file: quick-ref.md
+      - file: directives.md
       - file: headings.md
       - file: admonitions.md
       - file: agent-skill.md
@@ -123,7 +124,6 @@ toc:
       - file: conditionals.md
       - file: contributors.md
       - file: csv-include.md
-      - file: directives.md
       - file: dropdowns.md
       - file: definition-lists.md
       - file: example_blocks.md

docs/syntax/directives.md

@@ -1,4 +1,4 @@
-# Directives
+# How directives work
 
 Directives extend Markdown with additional features:
 

docs/syntax/index.md

@@ -12,7 +12,7 @@ Elastic Docs V3 uses a custom implementation of [MyST](https://mystmd.org/) (Mar
 
 If you know [Markdown](https://commonmark.org), you already know most of what you need. If not, the CommonMark project offers a [10-minute tutorial](https://commonmark.org/help/). 
 
-When you need more than basic Markdown, you can use [directives](directives.md) to add features like callouts, tabs, and diagrams.
+When you need more than basic Markdown, you can use _directives_ to add features like callouts, tabs, and diagrams. To learn how directives work in general, including how to add options and arguments and nest multiple directives, refer to [How directives work](directives.md). For a full list of available directives, refer to the sidebar.
 
 ## GitHub Flavored Markdown support