Add preliminary docs

Author: cotti

docs/_docset.yml

@@ -70,6 +70,7 @@ toc:
           - file: products.md
           - file: versions.md
           - file: legacy-url-mappings.md
+          - file: synonyms.md
       - folder: content-set
         children:
           - file: index.md

docs/configure/site/index.md

@@ -16,6 +16,10 @@ Configure the documentation site in these files:
 
 Redirects are also configured at the site-level. See [](../../contribute/redirects.md) for more information.
 
+## Synonyms
+
+Synonyms applied to our Serverless observability project are declared as a site-level configuration. See [](../../contribute/synonyms.md) for more information.
+
 ## V3 site-level diagram
 
 *Coming soon*

docs/configure/site/synonyms.md

@@ -0,0 +1,12 @@
+# `synonyms.yml`
+
+The [`synonyms.yml`](https://github.com/elastic/docs-builder/blob/main/config/synonyms.yml) file provides a way to define synonyms for our Serverless observability project. 
+
+Synonyms updates are sent during Elasticsearch-specific export procedures in the CI workflow.
+
+```yml
+synonyms:
+  - [ ".net", "c#", "csharp", "dotnet", "net" ]
+  - [ "esql", "es|ql" ]
+  - [ "motlp", "managed otlp" ]
+  ```