add design doc of market / 添加market设计文档

[elvin-du]

链服务模块 / Chain Service Components

• venus
• venus-auth
• venus-gateway
• venus-messager
• venus-miner
• 文档 / docs

订单服务模块 / Deal Service Components

• venus-market
• 文档 / docs

算力服务模块 / Storage Power Service Components

• venus-sector-manager
• venus-worker
• 文档 / docs

描述 / Description

增加market相关的软件设计文档