Readme update

README.md

@@ -14,9 +14,10 @@ Prerequisites:
 - the [json-c](https://github.com/json-c/json-c) development library
 - a POSIX.1-2008 compatible system (i.e. not MS Windows)
 
-For the module x11, you will need the folowing prerequisites:
+For the module x11 and sdl2, you will need the folowing prerequisites:
 
 - the [mpv](https://mpv.io/) development library
+- the [sdl2](https://www.libsdl.org/) development library
 - you will need `x11` for the default window module
 
 You will also need the following executables, with their path setted in the
@@ -43,6 +44,12 @@ You may need to put the `lib_window_x11.so` in the right directory to have the
 lektor player actually playing something (see the ini file). This path can be
 setted manually in the INI file.
 
+On archlinux, you need only to install the package:
+
+```sh
+makepkg -si
+```
+
 ## Preparing a kara for lektor
 
 A karamaker needs at least python3, with `mkvpropedit` (often installed with the