Add CNCF OpenTelemetry to CHANGELOG
### New features
+* CNCF OpenTelemetry source, sink and `cncf::otel` tremor-script library adds log, trace, metrics OpenTelemetry support
* Removed the vsn.sh script which checks if the lockfile is up to date and replaces it with the --locked flag [#798](https://github.com/tremor-rs/tremor-runtime/pull/798)
* Allow using '_' as seperators in numeric literals [#645](https://github.com/tremor-rs/tremor-runtime/issues/645)
* Refactor kafka metadata variables to be under a single record `$kafka`.
