docs: flesh out README

README.md

@@ -1,2 +1,20 @@
 # c-plus-plus
-Vài project vui vui viết bằng cpp
+
+Assorted small C++ hobby projects and experiments.
+
+## Contents
+
+| Folder | Description |
+|--------|-------------|
+| `Dai So Tuyen Tinh/` | Linear algebra exercises |
+| `Project/1` – `Project/5` | Numbered project exercises |
+
+Open any folder in your C++ IDE or compile with:
+
+```bash
+g++ <file>.cpp -o app && ./app
+```
+
+## License
+
+Apache-2.0 — see [LICENSE](LICENSE).