Update CODEOWNERS (#181)

* Update CODEOWNERS

adding a backup for TPP files, removing Ranu from doc

* Update CODEOWNERS

added 1 more person per offline request

Author: Maria1Petrova

.github/CODEOWNERS

@@ -1,10 +1,10 @@
 # Documentation owners and reviewers
-doc/        @Maria1Petrova @ranukund @maciekpac
-*.md        @Maria1Petrova @maciekpac
+doc/        @Maria1Petrova @maciekpac @nikitaxgusev
+*.md        @Maria1Petrova @maciekpac @nikitaxgusev
 man/        @nikitaxgusev @srirajpaul @maciekpac
 
 # TTP files
-third-party*    @Maria1Petrova
+third-party*    @Maria1Petrova @maciekpac @nikitaxgusev
 
 # Tests & examples
 tests/    @nikitaxgusev @srirajpaul