feat(docs): add mongo-sink usage on io docs

[ericsyh]

Motivation

Add mongo-sink step-by-step usage docs.

Modifications

Add mongo-sink step-by-step usage docs.

Verifying this change

• Make sure that the change passes the CI checks.

(Please pick either of the following options)

This change is a trivial rework / code cleanup without any test coverage.

(or)

This change is already covered by existing tests, such as (please describe tests).

(or)

This change added tests and can be verified as follows:

(example:)

• Added integration tests for end-to-end deployment with large payloads (10MB)
• Extended integration test for recovery after broker failure

Does this pull request potentially affect one of the following parts:

If yes was chosen, please highlight the changes

• Dependencies (does it add or upgrade a dependency): (no)
• The public API: (no)
• The schema: (no)
• The default values of configurations: (no)
• The wire protocol: (no)
• The rest endpoints: (no)
• The admin cli options: (no)
• Anything that affects deployment: (no)

Documentation

Check the box below or label this PR directly (if you have committer privilege).

Need to update docs?

• doc-required

  (If you need help on updating docs, create a doc issue)

• no-need-doc

  (Please explain why)

• doc

  (If this PR contains doc changes)

[Anonymitaet]

Hi @gaoran10 can you review this PR from the technical perspective? Then writers can review it from the technical writing perspective, thanks.

[github-actions]

The pr had no activity for 30 days, mark with Stale label.

[github-actions]

The pr had no activity for 30 days, mark with Stale label.

[tisonkun]

Closed as stale and conflict. Please rebase and resubmit the patch if it's still relevant.