Add openSUSE prerequisite instructions

These instructions were tested on openSUSE Tumbleweed and openSUSE Leap
15.1. There are some modules left that are not documented yet, but this
already improves the sitution for common openSUSE users.

modules/lang/cc/README.org

@@ -11,6 +11,7 @@
   - [[#irony-server][irony-server]]
     - [[#macos][MacOS]]
     - [[#arch-linux][Arch Linux]]
+    - [[#opensuse][openSUSE]]
   - [[#rtags][rtags]]
 - [[#configure][Configure]]
   - [[#project-compile-settings][Project compile settings]]
@@ -93,6 +94,11 @@ rm -rf irony-mode
 pacman -S clang cmake
 #+END_SRC
 
+*** openSUSE
+#+BEGIN_SRC sh :dir /sudo::
+sudo zypper install clang cmake
+#+END_SRC
+
 ** rtags
 Code navigation requires an [[https://github.com/Andersbakken/rtags][rtags]] server (~rdm~) installed. This should be
 available through your OS's package manager.