readme: added build instructions

Author: arteniioleg

README.md

@@ -1,7 +1,23 @@
-# OpenGL Snake Game
+# Snake Game [Download](https://github.com/arteniioleg/snake-game-opengl/releases)
 
-Huge thanks to [LearnOpenGL](https://github.com/JoeyDeVries/LearnOpenGL)!!!
+![gif](https://static.md/5e5b6d1fe1162905dc2a13710d74a420.gif)
 
-I was dreaming of being able to write 3D apps [since I was in high-school](https://github.com/arteniioleg/pascal-games) and here is my first 3D game!
+### Build
 
-![gif](https://static.md/5e5b6d1fe1162905dc2a13710d74a420.gif)
+1. Open IDE in docker by executing
+
+    ```bash
+    ./docker/ide.sh ~/path/to/ide.sh
+    ```
+
+    Check `x11docker` output about video driver install.
+
+2. Build target `external_all`
+3. Reload CMake
+4. Build target `snake_game_opengl`
+
+##### P.S.
+
+Huge thanks to [LearnOpenGL](https://github.com/JoeyDeVries/LearnOpenGL)!!!
+
+I was dreaming of being able to write 3D apps [since I was in high-school](https://github.com/arteniioleg/pascal-games) and this is my first 3D game!