Mysql-to-sqlite3

* [FEAT] add feature to transfer tables without any data (DDL only)

* [CHORE] add Python 3.10 support
* [CHORE] add Python 3.10 tests

* [FEAT] transfer JSON columns as JSON

* [CHORE] add experimental tests for Python 3.10-dev
* [CHORE] add tests for MariaDB 10.6

* [FIX] pin Click to <8.0

* [FEAT] add -K, --prefix-indices CLI option to prefix indices with table names. This used to be the default behavior
until now. To keep the old behavior simply use this CLI option.