readme: add build instructions

README.md

@@ -18,3 +18,16 @@ listener {
  - wayland
  - wayland-protocols
  - hyprlang >= 0.4.0
+
+# Building & Installation
+
+Building:
+```sh
+cmake --no-warn-unused-cli -DCMAKE_BUILD_TYPE:STRING=Release -S . -B ./build
+cmake --build ./build --config Release --target hypridle -j`nproc 2>/dev/null || getconf NPROCESSORS_CONF`
+```
+
+Installation:
+```sh
+sudo cmake --install build
+```