Rewrites CONTRIBUTING.md into a single, concise "Sending a pull request" flow (fork → install → branch + checks → commit + PR).
Adds an explicit upstream remote step, documents the git-hook–enforced branch/commit conventions, and notes that there is no test suite so changes are verified manually.
Also tidies the Contributing section formatting in README.md / README.ko.md to match.
N/A
npm run format:check — docs are Prettier-clean.feat:, fix:, chore:, refactor:, docs:, i18n:)locales/ko.json and locales/en.json (if UI text changed)