Add CODEOWNERS file for dsk (#781)

Author: ihrpr

.github/CODEOWNERS

@@ -0,0 +1,11 @@
+# TypeScript SDK Code Owners
+
+# Default owners for everything in the repo
+* @modelcontextprotocol/typescript-sdk-maintainers
+
+# Auth team owns all auth-related code
+/src/server/auth/ @modelcontextprotocol/typescript-sdk-auth
+/src/client/auth* @modelcontextprotocol/typescript-sdk-auth
+/src/shared/auth* @modelcontextprotocol/typescript-sdk-auth
+/src/examples/client/simpleOAuthClient.ts @modelcontextprotocol/typescript-sdk-auth
+/src/examples/server/demoInMemoryOAuthProvider.ts @modelcontextprotocol/typescript-sdk-auth