add the Market On Close order

[gnzsnz]

I have quite a few order types as discribed by TWS API documentation, implemented with ib_insync. if there is an interest on this, which this PR is a sign of it. I can contribute with the order types that i have.

just let me know

[zdytch]

Type hints needed, as the library is all type hinted

[mattsta]

I think the main feedback is there are 50+ different order types (https://www.interactivebrokers.com/en/index.php?f=4985) so the choices are:

• do we implement and maintain and document all of them
• or just let people use what they want and read the IBKR docs to populate the Order() fields themselves

Obvious examples are here, but the more detailed order types require so many custom fields it would be a full time job to implement and document them properly in our own API wrappers:

• https://interactivebrokers.github.io/tws-api/basic_orders.html
• https://interactivebrokers.github.io/tws-api/ibalgos.html