docs(microservices): add subscribe option to kafka docs

[theabuitendyk]

PR Checklist

Please check if your PR fulfills the following requirements:

• The commit message follows our guidelines: https://github.com/nestjs/docs.nestjs.com/blob/master/CONTRIBUTING.md

PR Type

What kind of change does this PR introduce?

[ ] Bugfix
[x] Feature
[ ] Code style update (formatting, local variables)
[ ] Refactoring (no functional changes, no api changes)
[ ] Build related changes
[ ] Other... Please describe:

What is the current behavior?

Issue Number: nestjs/nest#3739

What is the new behavior?

KafkaOptions includes support for the kafka.js subscribe fromBeginning option.

Does this PR introduce a breaking change?

[ ] Yes
[x] No

Other information

See related PR: nestjs/nest#4146