docs(sdk-metrics): fix badge and reword introductory sentence (#3484)

Author: pichlermarc

packages/sdk-metrics/README.md

@@ -3,7 +3,7 @@
 [![NPM Published Version][npm-img]][npm-url]
 [![Apache License][license-image]][license-image]
 
-OpenTelemetry metrics module contains the foundation for all metrics SDKs of [opentelemetry-js](https://github.com/open-telemetry/opentelemetry-js).
+This module contains the Metrics SDK of [opentelemetry-js](https://github.com/open-telemetry/opentelemetry-js).
 
 Used standalone, this module provides methods for manual instrumentation of code, offering full control over recording metrics for client-side JavaScript (browser) and Node.js.
 
@@ -89,4 +89,4 @@ Apache 2.0 - See [LICENSE][license-url] for more information.
 [license-url]: https://github.com/open-telemetry/opentelemetry-js/blob/main/LICENSE
 [license-image]: https://img.shields.io/badge/license-Apache_2.0-green.svg?style=flat
 [npm-url]: https://www.npmjs.com/package/@opentelemetry/sdk-metrics
-[npm-img]: https://badge.fury.io/js/%40opentelemetry%2Fmetrics.svg
+[npm-img]: https://badge.fury.io/js/%40opentelemetry%2Fsdk%2Dmetrics.svg