[DOCS] Getting started with ES|QL queries guide (#101634) (#101775)

* Page structure

* More getting started content

* Fix build errors

* Small improvements

* Typo

* Add link to public demo environment

* Review feedback

* Update docs/reference/esql/esql-get-started.asciidoc



* Review feedback

---------

Co-authored-by: Andrei Stefan <[email protected]>

Author: abdonpijpelink

docs/reference/esql/esql-commands.asciidoc

@@ -5,6 +5,7 @@
 <titleabbrev>Commands</titleabbrev>
 ++++
 
+[[esql-source-commands]]
 // tag::source_commands[]
 ==== Source commands
 
@@ -20,6 +21,7 @@ image::images/esql/source-command.svg[A source command producing a table from {e
 
 // end::source_command[]
 
+[[esql-processing-commands]]
 // tag::proc_commands[]
 ==== Processing commands