docs: add `README.md` and `CONTRIBUTING.md`

.vscode/extensions.json

@@ -0,0 +1,7 @@
+{
+  "recommendations": [
+    "editorconfig.editorconfig",
+    "stylelint.vscode-stylelint",
+    "ecmel.vscode-html-css"
+  ]
+}

CONTRIBUTING.md

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+# Contributing
+
+This document describes contribution guidelines for `x-markdown-css`.
+
+## Coding Style
+
+The project `x-markdown-css` uses [Stylelint](https://stylelint.io) to manage the SCSS coding style in a holistic way. In the meantime, please:
+
+- **DO** give priority to the current style of the project or file you're changing even if it diverges from the general guidelines or your preferences.
+- **DO NOT** send PRs for style changes. For example, do not send PRs that are focused on changing `.stylelintrc` rules.
+- **DO NOT** send PRs for upgrading code to use newer language features, though it's ok to use newer language features as part of new code that's written.
+- **DO NOT** send PRs for linting existing code.
+
+## Pull Requests
+
+- **DO** submit all code changes via pull requests (PRs) rather than through a direct commit. PRs will be reviewed and potentially merged by the repo maintainers after a peer review that includes at least one maintainer.
+- **DO** give PRs short-but-descriptive names (e.g. "Fix layout drift (solve #123)", not just "Solve issue #123")
+- **DO** refer to any relevant issues, and include [keywords](https://help.github.com/articles/closing-issues-via-commit-messages) that automatically close issues when the PR is merged.
+- **DO** tag any users that should know about and/or review the change.
+- **DO** ensure each commit successfully builds and passes Stylelint. The entire PR must pass all tests in the Continuous Integration (CI) system before it'll be merged.
+- **DO** address PR feedback in an additional commit(s) rather than amending the existing commits, and only rebase/squash them when necessary.  This makes it easier for reviewers to track changes.
+- **BE CAREFUL OF** submitting "work in progress" PRs. Generally, a PR should only be submitted when it is considered ready for review and subsequent merging by the contributor.
+- **DO NOT** send PRs only for changing build environments (begins with `chore:`), although the tool(s) might be outdated.
+- **DO NOT** fix merge conflicts using a merge commit. Prefer `git rebase`.
+- **DO NOT** mix independent, unrelated changes in one PR. Separate real product/test code changes from larger code formatting/dead code removal changes. Separate unrelated fixes into separate PRs, especially if they are in different partials.
+- *The last one and also the most important*: **DO NOT** destroy the existing codebase.

README.md

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+<h1 align="center">x-markdown-css</h1>
+
+<center>
+
+[![Version](https://img.shields.io/npm/v/x-markdown-css.svg)](https://www.npmjs.com/package/x-markdown-css)
+[![Node.js Requirement](https://img.shields.io/badge/node-%3E%3D16-blue.svg)](https://github.com/kuohuanhuan/x-markdown-css/blob/master/package.json)
+[![MIT License](https://img.shields.io/github/license/kuohuanhuan/x-markdown-css)](https://github.com/kuohuanhuan/x-markdown-css/blob/master/LICENSE)
+
+</center>
+
+> A simple and customizable Markdown CSS for everyone.
+
+## Requirement
+
+- Node.js >=16
+
+## Install
+
+```sh
+npm install
+```
+
+## Build
+
+```sh
+npm run build
+```
+
+## Usage
+
+You can use the minified CSS file with a CDN service:
+
+- UNPKG: `https://unpkg.com/x-markdown-css@latest/dist/bundle.min.css`
+- jsDelivr: `https://fastly.jsdelivr.net/npm/x-markdown-css@latest/dist/bundle.min.css`
+- CDNJS: *Coming soon. **Waiting for you to make `x-markdown-css` [popular enough](https://github.com/cdnjs/packages/blob/master/CONTRIBUTING.md#policy-rules-and-guidelines)**!*
+
+> *ps. `bundle.css` without `.min` stands for unminified version.*
+
+## Uses
+
+- [SCSS](https://sass-lang.com): CSS pre-processor.
+- [Grunt](https://gruntjs.com): Automating build tasks.
+- [PostCSS](https://postcss.org): Transforming CSS dist.
+- [Stylelint](https://stylelint.io): Linting SCSS codes.
+
+*...and much more.*
+
+## Contributing
+
+PRs, issues and feature requests are welcome!  
+Feel free to check [Issues](https://github.com/kuohuanhuan/x-markdown-css/issues) page. You can also take a look at the [Contributing Guide](https://github.com/kuohuanhuan/x-markdown-css/blob/master/CONTRIBUTING.md).
+
+## License
+
+Copyright (c) 2023 [kuohuanhuan](https://github.com/kuohuanhuan), licensed under [MIT](https://github.com/kuohuanhuan/x-markdown-css/blob/master/LICENSE).