Write docs/ceramic-stack

[michaelsena]

- Ceramic stack:
  - Intro to the stack: docs/ceramic-stack/introduction-to-the-stack.md
  - Stream programs:
    - docs/ceramic-stack/stream-programs/index.md
    - Stream program libraries: index.md
  - Data models:
    - docs/ceramic-stack/data-models/index.md
    - Data model libraries: index.md
    - Deploying data models: index.md
    - Composability: docs/ceramic-stack/data-models/composability.md
  - Client APIs:
    - docs/ceramic-stack/client-apis/index.md
    - Ceramic APIs:
      - docs/ceramic-stack/client-apis/ceramic/index.md
      - Ceramic JavaScript APIs: docs/ceramic-stack/client-apis/ceramic/javascript.md
      - Ceramic HTTP API: docs/ceramic-stack/client-apis/ceramic/http-api.md
    - Account APIs: 
      - docs/ceramic-stack/client-apis/accounts/index.md
      - Account JavaScript APIs: docs/ceramic-stack/client-apis/accounts/javascript.md
  - Development frameworks: docs/ceramic-stack/development-frameworks.md