[Docs] Add link to dependencies page - 8.x (elastic#214667)

## Summary

This PR adds a page to the 8.x Kibana docs linking to the list of
third-party dependencies.

Closes: elastic#212706
Rel: elastic#214668,
[elastic#797](elastic/docs-content#797)

---------

Co-authored-by: florent-leborgne <[email protected]>

Author: wajihaparvez

docs/developer/dependencies-versions.asciidoc

@@ -0,0 +1,4 @@
+[[dependencies-versions]]
+== List of dependencies
+
+Refer to https://artifacts.elastic.co/reports/dependencies/dependencies-current.html[Elastic Stack third-party dependencies] for the complete list of dependencies.

docs/developer/index.asciidoc

@@ -15,6 +15,7 @@ running in no time. If you have any problems, file an issue in the https://githu
 * <<kibana-architecture>>
 * <<advanced>>
 * <<plugin-list>>
+* <<dependencies-versions>>
 * <<development-telemetry>>
 
 --
@@ -33,5 +34,7 @@ include::advanced/index.asciidoc[]
 
 include::plugin-list.asciidoc[]
 
+include::dependencies-versions.asciidoc[]
+
 include::telemetry.asciidoc[]