Markdown writing standards

• Name files in lowercase-kebab-case: getting-started.md, api-reference.md
• Conventional UPPERCASE names at the repo root: README.md, CHANGELOG.md, CONTRIBUTING.md, LICENSE, CODE_OF_CONDUCT.md, SECURITY.md
• UTF-8, LF line endings, one trailing newline, no trailing spaces
• Keep images in an images/ or assets/ folder next to the docs and link them relatively

Write for the raw reader too: a well-formatted .md file should be easy to read in a terminal or a diff, not only when rendered. Enforce the rules automatically with markdownlint + Prettier (see Lint & format Markdown).