Add example for capturing changes from multiple SQL Server databases [DBZ-4803]

[jpechane]

Migrated from DBZ-4803

With DBZ-4783 in place, it's now possible to capture changes from multiple logical DBs on the same physical SQL Server host using one connector. The required config is shown in [this PR|https://github.com/debezium/debezium/pull/3261]. I suggest we create a separate example along those lines.

[akasar9]

@jpechane can you assign me this issue it's example/doc work good to start