Adds documentation for Firebird support

[makssent]

Fixes #33782.

Changes proposed in this pull request:

• Adds documentation for Firebird support

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• My code follows the code of conduct of this project.
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• I have made corresponding changes to the documentation.
• I have added corresponding unit tests for my changes.
• I have updated the Release Notes of the current development version. For more details, see Update Release Note

[makssent]

IDK if this entry will be correct in the documentation, as it differs from the others that use standard Testcontainers, but still.