Add readme

util/readme.md

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+This folder provides utility files for the pigpio library.
+
+### pigpiod
+
+`pigpiod` is a script that allows to run pigpiod as a Linux service with root privileges.
+The advantage of running pigpiod as a service is that pigpiod can be automatically launched on system startup.
+To automatically start pigpiod as a service, do the following:
+
++ Copy `pigpiod` from this directory to `/etc/init.d/`.
+
++ Make it executable: 
+  ```
+  sudo chmod +x /etc/init.d/pigpiod
+  ```
+
++ Tell update-rc.d to automatically start the pigpiod service on system startup:
+  ```
+  sudo update-rc.d skeleton defaults
+  ```
+  
++ Now, you can start, stop, and restart pigpiod using
+  ```
+  sudo service pigpiod start
+  sudo service pigpiod stop
+  sudo service pigpiod restart
+  ```
+
+
+### Findpigpio.cmake
+
+`Findpigpio.cmake` is a script used by CMake to find out where the pigpio header and library files are located.