Add DEVELOPMENT.md

[halsk]

Is your feature request related to a problem? Please describe.

It's good to put DEVELOPMENT.md as information for developers.

Describe the solution you'd like

I am refactoring the codebase now. I will write the documents after it.

The content would include:

Guidelines

reference to Code of Conduct

Branching rule

use feature/{issue id}-title

Accepting criteria

• [ ] Refer existing issue ID (If there is no issue, create it before sending pull request)
• [ ] Write test code

Directory structure

├── __test__   # test cases
├── docs    # documents
├── public   # public resources
├── src        # react source should be located here
│   ├── components    # components dir based on atomic design
│   │   ├── atoms          # basic building blocks 
│   │   ├── molecules   # smallest fundamental units of a compound.
│   │   └── organisms #  groups of molecules contains domain context
│   ├── hooks             # custom hooks
│   ├── pages              # pages represent URL
│   ├── services         # API services
│   ├── theme             # themes
│   ├── types              # type definitions
│   └── utils              # common utilities
└── supabase        # supabase logics here
    └── migrations       # migration files created by `supabase db commit`

test

How to write test

Translations

How to create/translate i18n resouces