feat: Add JSON type

[akkuman]

• fixes Does support json field ORM？ #199

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.

[franz101]

How do you access a key value?
text(column['a'])?

[akkuman]

How do you access a key value? text(column['a'])?

This is due to clickhouse restrictions so it cannot be accessed.
clickhouse queries for json type fields actually return tuples of values

If you want to access, you can only use toJSONString to convert to a string, then deserialize json to access, or use https://clickhouse.com/docs/en/sql-reference/functions/json-functions directly

[akkuman]

How do you access a key value? text(column['a'])?

maybe you can use https://clickhouse.com/docs/en/sql-reference/data-types/object-data-type#displaying-json-columns