feat: Add NGINXaaS for Azure team as CODEOWNERS for their documentation (#240)

This commit updates the CODEOWNERS file to add lines for the n4a-docs
team, responsible for maintaining the documentation for NGINXaaS for
Azure.

Author: ADubhlaoich

.github/CODEOWNERS

@@ -29,6 +29,10 @@ content/nap-dos/*           @nginx/dos-docs-approvers
 content/nap-waf/*           @nginx/nap-docs-approvers
 data/nap-waf/*              @nginx/nap-docs-approvers
 
+# NGINXaaS for Azure 
+content/nginxaas-azure/*          @nginx/n4a-docs
+content/includes/nginxaas-azure/* @nginx/n4a-docs
+
 # NGINX Gateway Fabric
 content/ngf/*               @nginx/nginx-gateway-fabric
 content/includes/ngf/*      @nginx/nginx-gateway-fabric