bug: mark "Stdout Exporter" as an incubator feature

[hedhyw]

Configuration:

telemetry:
  exporters:
    stdout:
      type: stdout

Zilla@0.9.74 prints:

At least one of the following sets of problems must be resolved.
zilla-1  | 1) [143,18][/telemetry/exporters/stdout/type] The value must be one of ["prometheus"].
zilla-1  | 2) [143,18][/telemetry/exporters/stdout/type] The string value must match the pattern "\$\{\{[\h\f\n\r\u000b?\u2028\u2029\ufeff]*([^[\h\f\n\r\u000b?\u2028\u2029\ufeff]\}]*)\.([^[\h\f\n\r\u000b?\u2028\u2029\ufeff]\}]*)[\h\f\n\r\u000b?\u2028\u2029\ufeff]*\}\}".

And it works if incubator features are enabled: https://docs.aklivity.io/zilla/latest/how-tos/install.html#enable-incubator-features

It's probably better to indicate this on the following page: https://docs.aklivity.io/zilla/latest/reference/config/telemetry/exporters/exporter-stdout.html

[vordimous]

Thank you for reporting this. The fix is on it's way.