chore: updating compatibility matrix (#2021)

Author: obecny

README.md

@@ -48,6 +48,7 @@ This is the JavaScript version of [OpenTelemetry](https://opentelemetry.io/), a
 
 | API Version | Core version | Contrib Version         |
 | ----------- |--------------|-------------------------|
+| v1.0.0-rc.0 | ------       | ------                  |
 | 0.18.x      | 0.18.x       | 0.14.x                  |
 |             | 0.17.x       | ------                  |
 |             | 0.16.x       | ------                  |