chore: Add tech writer to codeowners 2.x (#3525)

Updating codeowners file for 2.x so I can stalk the documentation
folder.

## Backport

#3524

Author: jabbacakes

.github/CODEOWNERS

@@ -9,3 +9,4 @@ AssemblyInfo.cs @NoelStephensUnity @EmandM @Unity-Technologies/netcode-qa
 .gitignore @NoelStephensUnity @EmandM @Unity-Technologies/netcode-qa
 .github/ @NoelStephensUnity @EmandM @Unity-Technologies/netcode-qa
 .yamato/ @NoelStephensUnity @EmandM @Unity-Technologies/netcode-qa
+com.unity.netcode.gameobjects/Documentation*/ @jabbacakes