chore: update codeowners to make new service shared

Author: Jwhiles

.github/CODEOWNERS

@@ -114,6 +114,7 @@
 /packages/remote-feature-flag-controller        @MetaMask/extension-platform @MetaMask/mobile-platform @MetaMask/core-platform
 /packages/storage-service                       @MetaMask/extension-platform @MetaMask/mobile-platform @MetaMask/core-platform
 /packages/client-controller                     @MetaMask/core-platform @MetaMask/extension-platform @MetaMask/mobile-platform
+/packages/cash-account-service                  @MetaMask/accounts-engineers @MetaMask/metamask-earn
 
 ## Package Release related
 /packages/account-tree-controller/package.json  @MetaMask/accounts-engineers @MetaMask/core-platform