Merge branch 'api-tags-doc' into 'master'

Add tags page to readme

The tags page was separated for the release feature but not to the index readme.

[ci skip]

See merge request !1861

doc/api/README.md

@@ -10,6 +10,7 @@
 - [Repositories](repositories.md)
 - [Repository Files](repository_files.md)
 - [Commits](commits.md)
+- [Tags](tags.md)
 - [Branches](branches.md)
 - [Merge Requests](merge_requests.md)
 - [Issues](issues.md)