Erg repository directory structure

  └─┬ assets: images, etc.
    ├─ CODE_OF_CONDUCT: Code of Conduct
    ├─┬ crates
    │ ├─ els: Erg Language Server
    │ ├─ erg_common: common utility
    │ ├─ erg_compiler: Compiler, **core of Erg**
    │ └─ erg_parser: Parser
    ├─┬doc
    │ ├─┬ EN
    │ │ ├─ API: Erg standard API
    │ │ ├─ compiler: About compiler implementation
    │ │ ├─ dev_guide: Guide for developers and contributors
    │ │ ├─ python: Python knowledge required for Erg development
    │ │ ├─ syntax: Erg syntax
    │ │ └─ tools: Erg command line tools
    │ └─┬ JA
    │ ...
    ├─ examples: sample code
    ├─ library: Erg script library
    ├─ src: directory where main.rs and driver are placed
    └─ tests: test code