Document the project

[bahmanm]

There's essentially no documentation about...well, anything 🤦

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List of topics that should be included as part of the codebase:

• What is bjForth?
  • Goals
  • Current status
  • Aspirations
• How is the code organised?
  • The holistic design and data model
  • Key components and terminology
  • Execution flow
• User's guide
  • Installation instructions
  • Well-annotated examples
• Contributor's guide
  • Development environment setup and libraries in use
  • The typical workflow: test ➡️ code ➡️ build ➡️ test
  • Test organisation
  • Example scenarios:
    • Add a new primitive
    • Extending/Fixing an existing primitive
    • Add new Forth words