CODEOWNERS fixes for Ecosystem

Create a section of the CODEOWNERS file for Ecosystem-related pages.
Reunite stray pages / directories under that umbrella, and make sure
they are assigned to the correct person. One line, even though it
doesn't actually belong to Ecosystem, had to go in the Ecosystem
section so Nick Gaskill would continue to get notifications.

.gitlab/CODEOWNERS

@@ -13,7 +13,6 @@
 /doc/.vale/ @marcel.amirault @eread @aqualls @cnorris
 /doc/administration/geo/ @axil
 /doc/administration/gitaly/ @eread
-/doc/administration/integration/ @aqualls
 /doc/administration/lfs/ @aqualls
 /doc/administration/monitoring/ @ngaskill
 /doc/administration/operations/ @axil @eread @marcia
@@ -36,7 +35,6 @@
 /doc/development/value_stream_analytics.md @msedlakjakubowski
 /doc/gitlab-basics/ @aqualls
 /doc/install/ @axil
-/doc/integration/ @aqualls @eread
 /doc/operations/ @ngaskill @axil
 /doc/push_rules/ @aqualls
 /doc/ssh/ @eread
@@ -65,8 +63,6 @@
 /doc/user/project/ @aqualls @axil @eread @msedlakjakubowski @ngaskill
 /doc/user/project/clusters/ @marcia
 /doc/user/project/import/ @ngaskill @msedlakjakubowski
-/doc/user/project/integrations/ @aqualls
-/doc/user/project/integrations/prometheus_library/ @ngaskill
 /doc/user/project/issues/ @msedlakjakubowski
 /doc/user/project/merge_requests/ @aqualls @eread
 /doc/user/project/milestones/ @msedlakjakubowski
@@ -142,6 +138,12 @@
 /doc/user/project/settings/import_export.md @aqualls
 /doc/user/snippets.md @aqualls
 
+[Docs Ecosystem]
+/doc/administration/integration/ @kpaizee
+/doc/integration/ @kpaizee
+/doc/user/project/integrations/ @kpaizee
+/doc/user/project/integrations/prometheus_library/ @ngaskill
+
 [Docs Growth]
 /doc/administration/instance_review.md @kpaizee
 /doc/api/invitations.md @kpaizee