[docs] Migrate docs from AsciiDoc to Markdown (#2635)

* delete asciidoc files

* add migrated files

* Apply suggestions from review

Co-authored-by: Josh Mock <josh@joshmock.com>

* Apply suggestions from review

Co-authored-by: Josh Mock <josh@joshmock.com>

* add the new ci checks (#2634)

---------

Co-authored-by: Marci W <333176+marciw@users.noreply.github.com>
Co-authored-by: Josh Mock <josh@joshmock.com>

docs/reference/integrations.md

@@ -0,0 +1,16 @@
+---
+mapped_pages:
+  - https://www.elastic.co/guide/en/elasticsearch/client/javascript-api/current/integrations.html
+---
+
+# Integrations [integrations]
+
+The Client offers the following integration options for you:
+
+* [Observability](/reference/observability.md)
+* [Transport](/reference/transport.md)
+* [TypeScript support](/reference/typescript.md)
+
+
+
+