chore: add beta badge to readme (#871)

README.md

@@ -3,6 +3,7 @@
 [![CircleCI][circleci-image]][circleci-url]
 [![Coverage Status][codecov-image]][codecov-url]
 [![Apache License][license-image]][license-image]
+[![Beta Badge][beta-image]][beta-image]
 
 ## About this project
 This is the JavaScript version of [OpenTelemetry](https://opentelemetry.io/), a framework for collecting traces, metrics and logs from applications.
@@ -156,6 +157,7 @@ Apache 2.0 - See [LICENSE][license-url] for more information.
 [codecov-image]: https://codecov.io/gh/open-telemetry/opentelemetry-js/branch/master/graph/badge.svg
 [codecov-url]: https://codecov.io/gh/open-telemetry/opentelemetry-js/branch/master/
 [license-image]: https://img.shields.io/badge/license-Apache_2.0-green.svg?style=flat
+[beta-image]: https://img.shields.io/badge/status-beta-informational?logo=data:image/png;base64,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
 
 [docs]: https://open-telemetry.github.io/opentelemetry-js