Introduce KafkaEngine support

[jimenezj8]

Adds limited official support for KafkaEngine as requested in this ticket. Although documentation was added for extending clickhouse-sqlalchemy with custom engines downstream, it would be beneficial to the community to add first-class support.

For now, this PR adds logic to the DDLCompiler in order to generate CREATE TABLE statements using the new engine. This is an experimental engine, as stated by the ClickHouse docs. Tables with this engine should also never be read from directly - the query will simply fail, as noted by ClickHouse docs.

Checklist:

• Add tests that demonstrate the correct behavior of the change. Tests should fail without the change.
• Add or update relevant docs, in the docs folder and in code.
• Ensure PR doesn't contain untouched code reformatting: spaces, etc.
• Run flake8 and fix issues.
• Run pytest no tests failed. See https://clickhouse-sqlalchemy.readthedocs.io/en/latest/development.html.

[jimenezj8]

@xzkostyan please let me know how to proceed with this PR, when you have the opportunity