docs: custom representation integration process

[pranaymohan]

It would help to have a section in docs that we could share with layer 1 / bridge teams around how to deploy custom representations and what they need to do to migrate liquidity. It would also help to discuss the tradeoffs of adopting a custom representation.

The target user is engineers working on another bridge or layer 1 with a native bridge, who has interest in making their representation fungible with Optics and other bridge representations