[Contracts] [Document] Liveness bond lockups

[AnshuJalan]

At the moment only the proposer can deposit liveness bond when proposing the blocks in Taiko. Since for the AVS the task manager is the sole proposer, we need to implement a separate accounting system for liveness bonds so that the operator may deposit and withdraw it from the task manager. This is non-trivial and deviates from the primary goal of devising a preconfirmations system. Therefore, this has been skipped in the POC. The liveness bond stays locked up in the TaikoL1 contract.