Add README with installation and build instructions

README.md

@@ -1,3 +1,40 @@
 # H7CAD
 
 <img width="1920" height="940" alt="resim" src="https://github.com/user-attachments/assets/25bc2bb2-c35c-477d-a3e9-45c86690b5c9" />
+
+A CAD application for 2D/3D drawing and design, built with Rust.
+
+## Features
+
+- 2D drafting and 3D modeling
+- DXF file import/export
+- GPU-accelerated rendering via WebGPU
+- Snap and annotation tools
+- Modular ribbon interface (Home, Annotate, Insert, View, Manage)
+
+## Installation
+
+### Flatpak (Linux)
+
+Download `H7CAD.flatpak` from the [latest release](https://github.com/HakanSeven12/H7CAD/releases/latest), then:
+
+```bash
+flatpak remote-add --if-not-exists flathub https://flathub.org/repo/flathub.flatpakrepo
+flatpak install H7CAD.flatpak
+flatpak run io.github.HakanSeven12.H7CAD
+```
+
+### Build from Source
+
+Requirements: Rust 1.75+
+
+```bash
+git clone https://github.com/HakanSeven12/H7CAD.git
+cd H7CAD
+cargo build --release
+./target/release/H7CAD
+```
+
+## License
+
+GPL-3.0-only — see [LICENSE](LICENSE)