chore: add agents.md

Author: Lancern

AGENTS.md

@@ -0,0 +1,29 @@
+# AGENTS.md
+
+You are building a static website that documents C/C++ language features and standard library facilities for C/C++ developers.
+
+## Project Structure
+
+- The `src/content/docs` subdirectory is where the documentation pages should go.
+  - Documentations for C language features go into `src/content/docs/c/language`.
+  - Documentations for C standard library facilities go into `src/content/docs/c/library`.
+  - Documentations for C++ language feature go into `src/content/docs/cpp/language`.
+  - Documentations for C++ standard library facilities go into `src/content/docs/cpp/library`.
+- The `src/components` contains reusable UI components for the documentation pages.
+
+## Development Guidelines
+
+- Each paragraph should generally be a single line of source code.
+- Avoid writing source code that does not contribute to actual content as much as possible, extract layout code into reusable components when possible.
+- Avoid inline Markdown tables with more than 3 columns.
+- When designing content layout, consider layout on mobile devices as a first-class usage.
+
+## Code Style
+
+- Use double quotes in MDX, JavaScript, TypeScript code.
+- Always prefer TypeScript over JavaScript when possible.
+- Use explicit semicolons in JavaScript and TypeScript code.
+
+## Development Tools
+
+- Run `npm run format` to format the code once you made any changes.