Add spec folder to each module

[shaolin-flow]

We need to document the design spec of each module in the x/ folder. The EVMOS team broke down specs in a clear and concise way, I recommend following their model, see here as an example. The completion of a spec should have the following information included:

• [ ] Abstract: What is the purpose of the module?
• [ ] Concepts: Key concepts broken down in detail
• [ ] State: Stateful objects
• [ ] State transitions: Description of state transitions in the module
• [ ] Transactions: Defining Msg types
• [ ] Hooks: Any registered hooks
• [ ] Events: Emitted events
• [ ] Parameters: Module level parameters
• [ ] Clients: CLI instructions
• [ ] Future improvements: Changes considered in the foreseeable future