Edit CDC examples to show more than one table in a changefeed

[lnhsingh]

Closes #6109

[cockroach-teamcity]

This change is 

[cockroach-teamcity]

Online preview: http://cockroach-docs-review.s3-website-us-east-1.amazonaws.com/65ecd047b7279af51b19b420e2b5e800e868e5e1/

Edited pages:

• v19.1/change-data-capture.md
• v19.2/create-changefeed.md
• v20.1/create-changefeed.md

[lnhsingh]

cc @mwang1026

[cockroach-teamcity]

Online preview: http://cockroach-docs-review.s3-website-us-east-1.amazonaws.com/b793f6fd59976923ca09fac7e6e5c246d0ee014b/

Edited pages:

• v19.1/change-data-capture.md
• v19.2/change-data-capture.md
• v19.2/create-changefeed.md
• v20.1/change-data-capture.md
• v20.1/create-changefeed.md

[cockroach-teamcity]

Online preview: http://cockroach-docs-review.s3-website-us-east-1.amazonaws.com/1be18c669723c52b7cd4e9f49b3a037aab59861f/

Edited pages:

• v19.1/change-data-capture.md
• v19.2/change-data-capture.md
• v19.2/create-changefeed.md
• v20.1/change-data-capture.md
• v20.1/create-changefeed.md

[cockroach-teamcity]

Online preview: http://cockroach-docs-review.s3-website-us-east-1.amazonaws.com/6bfed0746bc5c1001b060b7326fc33fdedd5be57/

Edited pages:

• v19.2/change-data-capture.md
• v19.2/create-changefeed.md
• v20.1/change-data-capture.md
• v20.1/create-changefeed.md

[danhhz]

Reviewable status: complete! 0 of 0 LGTMs obtained (waiting on @danhhz, @lnhsingh, and @piyush-singh)

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v19.2/change-data-capture.md, line 428 at r1 (raw file):

    {"after": {"id": 1, "name": "Petee H"}}
    {"after": {"id": 2, "name": "Carl"}}
    {"after": {"name": "Lauren", "rowid": 528514320239329281}}

where's the dog_id?

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v19.2/change-data-capture.md, line 612 at r1 (raw file):

    This will start up the changefeed in the background and return the `job_id`. The changefeed writes to Kafka.

14. In a new terminal, move into the extracted `confluent-<version>` directory and start watching the Kafka topic:

nit: topics

[lnhsingh]

Reviewable status: complete! 0 of 0 LGTMs obtained (waiting on @danhhz and @piyush-singh)

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v19.2/change-data-capture.md, line 428 at r1 (raw file):

Previously, danhhz (Daniel Harrison) wrote…

where's the dog_id?

Added.

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v19.2/change-data-capture.md, line 612 at r1 (raw file):

Previously, danhhz (Daniel Harrison) wrote…

nit: topics

Done.

[cockroach-teamcity]

Online preview: http://cockroach-docs-review.s3-website-us-east-1.amazonaws.com/62cae61fff6ac820694aa6b078fb42e856153f23/

Edited pages:

• v19.2/change-data-capture.md
• v19.2/create-changefeed.md
• v20.1/change-data-capture.md
• v20.1/create-changefeed.md

[ericharmeling]

LGTM

Reviewed 4 of 6 files at r1, 2 of 2 files at r2.
Reviewable status: complete! 0 of 0 LGTMs obtained (waiting on @danhhz and @piyush-singh)