chore: update client readme template (#1603)

Author: trivikr

codegen/smithy-aws-typescript-codegen/src/main/resources/software/amazon/smithy/aws/typescript/codegen/README.md.template

@@ -1,6 +1,6 @@
-${packageName}
+# ${packageName}
 
-[![NPM version](https://img.shields.io/npm/v/${packageName}/beta.svg)](https://www.npmjs.com/package/${packageName})
+[![NPM version](https://img.shields.io/npm/v/${packageName}/rc.svg)](https://www.npmjs.com/package/${packageName})
 [![NPM downloads](https://img.shields.io/npm/dm/${packageName}.svg)](https://www.npmjs.com/package/${packageName})
 
 For SDK usage, please step to [SDK readme](https://github.com/aws/aws-sdk-js-v3).