add global reviewer (#3889)

This PR adds a global catch all rule so the dotnet-docs team will be tagged for all PRs. That will prevent items from falling through the cracks.

Author: BillWagner

.github/CODEOWNERS

@@ -4,9 +4,11 @@
 # More details are here: https://help.github.com/articles/about-codeowners/
 
 # The '*' pattern is for global owners.
-# Not adding in this PR, but I'd like to try adding a global owner set with the entire team.
-# One interpretation of the GitHub docs is that global owners are added only if not removed
-# by a more local rule.
+
+# This line tags the dotnet-docs team for review, so nothing falls through the cracks.
+
+*     @dotnet/docs
+
 
 # Order is important. The last matching pattern has the most precedence.
 # The folders are ordered as follows: