Update CosmosDB codeowners (Azure#9867)

To get the users notified whenever a PR is created in CosmosDB

Author: MehaKaushik

CODEOWNERS

@@ -15,7 +15,7 @@
 /specification/containerinstance/ @novinc
 /specification/containerregistry/ @djyou
 /specification/containerservice/ @yangl900
-/specification/cosmos-db/ @dmakwana
+/specification/cosmos-db/ @dmakwana @MehaKaushik @wmengmsft @shurd
 /specification/customer-insights/ @tjlvtao
 /specification/datafactory/ @zhangyd2015
 /specification/datalake-analytics/ @ro-joowan