Filecoin Onchain Cloud docs

[longfeiWan9]

During Dubai Colo, we have decided to keep all the FOC-related docs together in one place, which will be combined with Synapse docs.

The docs structure will be:

Introduction
   - Overview
   - About the Filecoin Onchain Cloud
   - Why Filecoin Onchain Cloud

Getting Started
   - Quick Start 

Core Concepts
   - Architecture
   - PDP
   - Filecoin Pay
   - FWSS
 
Developers
   - Overview
   - Synapse SDK
        - Quick start
        - Payment
        - Storage
        - Monitoring

API
   - synapse SDK
   - pdp
   - Filecon Pay
   - Filecoin Beam
  
Resources
FAQ

Based on the above docs structure, we will break down the tasks into:

• Basic Docs strucutre Feat/foc docs #265
• Intro Docs: Introduction #322
• Getting Started Docs: Getting started #323
• Concepts
• Developer/Synapse-sdk
• API
• Resources
• FAQ