Update CODEOWNERS

Author: clarkd

.github/CODEOWNERS

@@ -13,6 +13,7 @@ plugins/Postcoder/*  @richbenwell
 plugins/RDAP/*  @richbenwell
 plugins/RSS/*  @clarkd
 plugins/Rootly/*  @noorulkhan-n
+plugins/SendGrid/*  @richbenwell
 plugins/Spotify/*  @jame2O
 plugins/Steam/*  @kmichalski0
 plugins/SumoLogic/*  @richpeters